7 Ways to Thicken up a Sauce

Did your soup turn out thin and runny? Having trouble getting gravy to the perfect consistency? Don't worry: We can teach you how to thicken sauce in all sorts of easy ways.

It happens to the best of us: You followed the recipe to a T, but it just didn’t turn out as you expected. Isn’t a gravy supposed to be thick enough to coat the back of a spoon? Shouldn’t an Alfredo sauce cling to the sides of the pasta noodles?

Professional recipe developers (including the folks in our Test Kitchen) try to anticipate everything, but sometimes other factors get in the way. Maybe you prefer your gravy a touch thicker than they do, or perhaps the amount of humidity in your kitchen affected the thickening power of your flour.

Use these tips and tricks to fix thin, runny soups and lackluster gravies without thinking twice.

1. Flour

If being gluten-free isn’t a concern, adding flour is a fantastic way to thicken dairy-based sauces, thick soups and gravies. My preferred method is to make a roux (a combination of equal parts fat and all-purpose flour) and whisk in 2 ounces for every cup of liquid. Since the flour is already cooked in the roux-making process, you won’t run the risk of the dish tasting like raw flour—or of making your family sick.

Alternatively, you can add a little water directly to raw flour, using about 2 tablespoons for every cup of liquid in your recipe. Whisk the slurry into the pot and simmer it for a few minutes, or until the sauce has thickened and the taste of flour is cooked out.

Keep in mind that flour will make your sauce cloudy, so if you need to maintain clarity while increasing the viscosity, the next thickener is a better option.

2. Cornstarch or arrowroot

Cornstarch and arrowroot are gluten-free alternatives to thickening with flour. They’ll also keep your sauce clear and cloud-free. You’ll need about 1 tablespoon for every cup of liquid in the recipe. Mix the cornstarch with equal parts water to create a slurry and pour it into the pot. Whisk continuously over high heat until the cornstarch is well incorporated and the sauce starts to thicken.

What’s the difference between the two? In a nutshell, arrowroot is naturally GMO-free and freezes better than cornstarch. It does become slimy when combined with dairy, though, so skip it as your gravy thickener.

3. Tomato paste

The best time to add tomato paste is at the beginning of the recipe—heating it releases the essential oils and also caramelizes the sugars—but you can whisk it in near the end to help tomato-based soups and sauces bind. You could also add it to brown sauces or beef stews, but since it adds a burst of color and tomato flavor, we wouldn’t recommend it for dairy-based sauces.

4. Reduce the liquid

If you have plenty of extra time, reducing the liquid down is a great way to thicken things up. As the liquid evaporates, the other flavors will concentrate, too, which may or may not be a good thing. Since simmering a huge stockpot of sauce can take a while, you could remove a portion of the sauce to a wide saute pan to speed things up a bit. Then, just stir it back into the main pot when it’s nice and thick.

5. Swirl in a pat of butter

This method won’t add a serious amount of thickness, but it will give you an extra boost if you’re close but not quite there. Just make sure to swirl the butter into your sauce at the very end of the cooking process. The butter-infused sauce will break if it’s exposed to high heat, defeating the purpose of its thickening power.

6. Add an egg yolk

Egg yolks are a classic way to thicken salad dressings and custards, but they also work wonders for thickening rich cream sauces. To prevent the egg from scrambling, place the egg yolk in a bowl and slowly whisk in about a cup of the hot sauce. Then, add the tempered yolk mixture to the pot, whisking as you go.

The egg yolk method also works really well as a way to save a broken sauce.

7. Puree some vegetables

Starchy vegetables—like potatoes, winter squash or celeriac—are excellent thickening agents, especially if they’ve been pureed. Simply roast or boil these vegetables and pop them into the food processor until smooth. Then, stir it into the sauce, and voila: It will instantly be thicker! You could also use steamed and mashed cauliflower, or any kind of cooked beans or lentils, keeping in mind that the latter would add additional flavors to the dish.

Depending on the type of recipe you’re making, you may also be able to puree half or more of your soup or sauce to thicken it up. It would reduce the dish’s chunky consistency, but it would thicken things up without introducing any extra ingredients.

Next time your sauce is a little thin, experiment with these solutions. You’re bound to find one that works for your recipe.

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Lindsay D. Mattison
After years of working in professional kitchens, Lindsay traded her knives in for the pen. While she spends most of her time writing these days, she still exercises her culinary muscles on the regular, taking any opportunity to turn local, seasonal ingredients into beautiful meals for her family.