How to Make the Milk Bar Birthday Cake Recipe (with Tips from Christina Tosi!)

Updated: Apr. 20, 2023

We got tips from Christina herself on how to make the best-ever confetti sheet cake. Spoiler alert: It tastes even better than it looks!

Every home cook and baker has their idol. Taste of Home staffer Caroline loves Julia Child and contributor Julia admires Ree Drummond. As for me, I’m a devoted fan of Christina Tosi, the founder of Milk Bar and Master Chef Junior judge. Christina is famous for her new takes on favorite flavors from childhood, like breakfast cereal-flavored treats, sweet-salty cookies and—my favorite—confetti cake.

When I saw her latest cookbook, All About Cake, had a recipe for her famous take on the confection made in a sheet pan, I had to try it. But before I could get mixing up this recipe, I got to chat with Christina a bit about her baking philosophy and tips for making beautiful treats at home.

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Q&A With Christina Tosi

Confetticake 7Lisa Kaminski/Taste of Home

What Makes a Good Dessert?

“Good food is good food,” Christina told me over the phone. And when it comes to good food, anything is fair game to Christina—not just the fanciest gourmet ingredients. In fact, the menu at Milk Bar and the recipes in her cookbooks read like a sugar-fueled fantasy: sprinkles, cake mix, chocolate chips, cornflakes and even potato chips (for that sweet-and-salty mix).

“These are the flavors that everyone can relate to,” she said. “The secret to a good dish comes from balance, not some far-fetched flavor combination no one’s ever heard of before.”

How to Make Milk Bar Treats at Home

As for creating Christina’s Milk Bar treats at home—or any homemade bake—Christina told me her most important piece of advice would be “starting from a place of humility.”

While Christina is an absolute pro (and winner of the prestigious James Beard Award twice over), she explains that she doesn’t like to get overly fussy in her baking. In fact, she prefers all her bakes to look “comfortably human.” In her books, you won’t find her calling for piping bags or hard-to-find tools. Instead, Christina relies on spoons, spatulas and kitchen basics to achieve this human (but still beautiful) look.

“A dessert should look like something you want to dive into,” she told me. “A great dessert should be an invitation to eat—not something that’s too pretty to slice into.”

With that advice, my mind was put at ease, and I was totally ready to tackle her confetti sheet cake recipe. Let’s get into it!

The Famous Milk Bar Birthday Cake Recipe

Lisa Kaminski/Taste of Home

The Cake

  • ½ cup butter, softened. Here’s how to do it quickly.
  • ½ cup shortening
  • 2 cups + 2 tablespoons sugar
  • 1/3 cup brown sugar, packed
  • 5 eggs
  • ¾ cup + 1 tablespoon buttermilk
  • ½ cup grapeseed or vegetable oil
  • 3½ teaspoons vanilla extract
  • 3½ cups cake flour
  • 1¼ cups rainbow sprinkles, divided
  • 2½ teaspoons baking powder
  • 1¼ teaspoons salt

Milk Soak

  • ½ cup whole milk
  • 2 teaspoons vanilla extract

Cake Crumbs

  • 1 cup + 1 tablespoon sugar
  • 1½ cup + 1 tablespoon cake flour
  • ¼ cup light brown sugar, packed
  • ¼ cup rainbow sprinkles
  • 1 teaspoon baking powder
  • 1 teaspoon salt
  • 1/3 cup + 2 tablespoons grapeseed or vegetable oil
  • 2 tablespoons vanilla extract

Fluffy Frosting

  • 1 cup butter, softened
  • ½ cup shortening
  • 4 ounces cream cheese, softened
  • 3 tablespoons light corn syrup
  • 2 tablespoon vanilla extract
  • 2½ cups confectioners’ sugar
  • 1 teaspoon salt
  • Pinch baking powder
  • Pinch citric acid—you can find this at specialty grocers for a few dollars; if you can’t find it, it’s OK to skip it!

Initial Thoughts

Looking at this recipe, it seems sort of daunting. Most sheet cakes are fairly simple, though crowd-pleasing. This one, on the other hand, consists of four different components. However, knowing Christina’s reputation for irresistible treats and next-level baking, I was confident that the combination of cake, frosting, crumbs and milk would make this a cake not to be missed. As Christina writes in her book All About Cake, this birthday sheet cake is the most popular at her bakeries: “People love to eat birthday-flavored cake when celebrating things, even when there’s not a birthday to honor in the room.”

If the thought of a four-step cake is still daunting, keep in mind that all parts can be prepped a few days in advance. No need for an all-day bake here! (If you’re looking for a bake to enjoy all day long, though, check out these recipes!)

Step 1: Kicking Off with Cake Crumbs

Lisa Kaminski/Taste of Home

Looking over the recipe for this cake, I decided to start with the birthday cake crumbs. These crumbs add a crunchy texture to the cake and are a signature element of all of Christina’s cakes. Since I love crunch, I was ready to give it a go.

Making these crumbs is fairly simple. Start by mixing the cake flour, brown sugar, light brown sugar, rainbow sprinkles, baking powder and salt together in a stand mixer on the low setting. You’re going to use a quarter cup of sprinkles for the crumbs alone (plus more than a cup for the cake), so I recommend buying these jimmies in bulk—you can find some here.

Once the dry ingredients are combined, add the grapeseed oil and vanilla extract and mix. This should form small clumps.

Pro tip: Don’t have grapeseed oil on hand? Christina writes in her book that you can substitute vegetable oil no problem.

From here, spread these confetti crumbs onto a lined sheet pan and bake for 20 minutes at 300ºF. Remove from the oven and break up any extra-large crumbs. They might be slightly soft to the touch when you pull them out, but they will harden after cooling. Be sure to let them cool all the way before using.

According to Christina, these will keep in an airtight container for about a week. If you pop them in the fridge or freezer and keep them for up to a month. Bear this in mind since this batch will make more cake crumbs than you need—though I sprinkled a lot of the extras over ice cream. It was fabulous.

Step 2: Making the Confetti Cake

Lisa Kaminski/Taste of Home

With the cake crumbs cooling, I moved onto the star of the show: the cake! Making this sheet cake is a bit involved, but I knew it would be worth it.

For this cake, start by creaming the softened butter, shortening, sugar and brown sugar together in a stand mixer set on medium-high speed for about three minutes. Be sure to scrape down the bowl halfway through the process and then again at the end. This should make a light and fluffy mixture.

Then add the eggs one at a time. Beat on medium-high speed for a minute after each addition. After adding the last egg—there are five altogether—scrape down the bowl and then beat the mix on high for another four minutes. It’s a little time consuming, but it’s worth it!

Now onto the wet ingredients. Combine the buttermilk, grapeseed oil and vanilla extract. Then, set your mixer on medium speed and stream this liquid into the mix slowly. I’m talking really really slowly. Christina writes that adding the liquid to batter should take about three minutes. Rushing the process could cause your batter to separate. Once the liquid is fully incorporated, scrape down the side of the bowl and then mix for another three minutes on medium-high.

In another bowl, whisk together the cake flour, one cup of rainbow sprinkles, baking powder and salt. With your stand mixer on low, slowly add the dry ingredients. Mix until this batter just comes together—about a minute. Again, scrape down the sides and mix again for another minute.

At this point, I noticed that this batter looked and smelled just like classic confetti cake mix twice as good. I had to take a little taste of the batter—it tasted ten times better than I could have imagined. After that small taste, I felt ready to bake this cake.

To do so, divide the batter evenly between two quarter-size sheet pans (that’s about 13×9″) sprayed with cooking spray and lined with parchment paper—I used our Test Kitchen’s favorite Nordic Ware pans. Use a spatula to spread the batter evenly, then top with the remaining quarter cup of sprinkles. Pop these in the oven for 30-35 minutes at 350ºF. When they’re ready, they should spring back slightly when touched.

Let the cakes cool completely in the pans on a wire rack before removing. You can wrap them up and store them in the fridge for up to five days.

Step 3: Whipping Up the Super Fluffy Frosting

Lisa Kaminski/Taste of Home

What’s a good cake without an equally amazing frosting? To make Christina’s trademark birthday frosting, start by combining two sticks of softened butter, a half cup of vegetable shortening and four ounces of cream cheese together in the bowl of a stand mixer. Beat this on medium-high speed for about three minutes. This will start to build the fluffy foundation of this frosting.

Then, with the mixer set to low, stream in three tablespoons of corn syrup and two tablespoons of vanilla extract. Once added, turn up the mixer to medium-high and let it go to work! After three minutes, it should look nice and shiny.

Give your bowl a quick scrape—you want everything well combined—add in your powdered sugar, salt, baking powder and citric acid. Mix this on low until combined just to avoid that dreaded sugar cloud. Once incorporated, crank up the speed to medium-high until the frosting is bright white and incredibly fluffy.

If you’re like me, those last two ingredients might throw you for a loop. When it comes to the citric acid, it adds a bit of tartness that cuts through all that sugar. You can find it in the canning section of some grocers. If you can’t find it, I wouldn’t sweat it too much! As for the baking powder, I was stumped. Our food editors suspect it helps prevent the syrup from crystallizing.

Whatever the case, this frosting turns out pure white and super fluffy. It looks a lot like whipped frosting from a can, only better than I could have imagined.

Step 4: What About the Milk Soak?

After putting together three cake components, a fourth might seem like too much. Good news here: The milk soak is just a half cup of whole milk and two teaspoons of vanilla stirred together. Simple! This soak will add extra moisture to the cake when layer it up.

Step 5: Putting It All Together

Lisa Kaminski/Taste of Home

Christina’s cakes have their own distinct style. No fussy decorating or frosting here. Rather Christina’s cakes are frosted simply and allow you to see every layer of the confetti creation. As for perfection, I remembered Christina’s words of wisdom: a good bake should be “comfortably human.”

Amen to that! I approached this cake with her perfectly imperfect mentality in mind.

To start putting this cake together, I laid down the first layer on a large cutting board (though, Christina writes in her book that a sheet pan lined with parchment works). With that first layer in place, brush half of the milk soak over the cake with a pastry brush. Don’t skip this—it will give the cake extra rich flavor and the moist texture you want.

Then using an offset spatula, spread a quarter of the fluffy, white frosting over the cake, making sure it’s nice and even. Then sprinkle a cup of those crunchy birthday cake crumbs over the top. Press them lightly into the frosting so they really stick—you don’t want them going anywhere because then you spread another quarter of your frosting over the top. If you’re keeping track the order is cake, milk soak, frosting, crumbs and more frosting.

Lisa Kaminski/Taste of Home

Then start the process over by carefully laying that second layer of cake on top. Coat with the remains of the milk soak and top with the rest of the frosting. You can frost with the back of a spoon to give this cake swoops and swirls. I opted to give it a nice smooth coat with my favorite OXO offset spatula. Top it all off with another cup of those crunchy cake crumbs and then pop this in the freezer for a few hours. Christina recommends 12 hours, but I only let it set two and the rest worked out fine (shhh… don’t tell her!).

After 12 (or just two) hours, remove the cake from the freezer. Use a sharp knife to cut off the very edges of the cake. This will allow you to see all those delicious layers and all the hard work (and you can snack on the scraps). As Christina told me during our chat, “it should look like something you want to dive into!”

How Did It Taste?

Lisa Kaminski/Taste of Home

After revealing every delicious layer and all those sprinkles, I definitely wanted to dive in. But looking at such a celebratory cake, I couldn’t go at it alone. I sliced it up and served it at Taste of Home HQ. So how did it taste?

This cake exceeded my expectations. The cake itself was like your classic confetti cake you remember from childhood but made magic. It was light in texture but still moisture thanks to that milk soak. That simple step added a lot of impact here—the cake was moister and had more vanilla flavor. Paired with the cake crumbs inside, I honestly couldn’t get enough. A bit of crunch inside gave this cake a different feel and it was a lot of fun to eat with all the layers.

Lisa Kaminski/Taste of Home

I will say, though, that the star of the show for me was this frosting! With two unexpected ingredients (citric acid and baking powder), I wasn’t so sure how it would taste. But let me tell you, it’s some of the best frosting I’ve ever tried. It’s fluffy and perfectly flavored (not to mention it was a breeze to frost with!). It’s one recipe that I’m keeping handy for topping off any cake—not just this birthday sheet cake.

While this cake definitely requires some extra work, I have to say for a special celebration it’s more than worth it!

Try these confetti treats, too!
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