Banana Flip Cake

Directions

1. Line 2 greased 15x10x1-in. baking pans with waxed paper and grease the paper. Set aside.
2. In a large bowl, combine the cake mix, pudding mix, milk and eggs. Beat on low speed for 30 seconds; beat on medium for 2 minutes.
3. Spread batter into prepared pans. Bake at 350° until a toothpick inserted in the centers come out clean, 12-15 minutes. Cool for 5 minutes before inverting onto wire racks to cool completely. Gently peel off waxed paper.
4. Meanwhile, in a small saucepan, whisk flour and milk until smooth. Bring to a boil; cook and stir until thickened, about 2 minutes. Remove from the heat; cover and cool to room temperature.
5. In the bowl of a heavy-duty stand mixer, cream the butter, shortening and sugar until light and fluffy, 5-7 minutes. Beat in vanilla. Add milk mixture; beat on high until fluffy, 10-15 minutes.
6. Place one cake on a large cutting board; spread top with frosting. Top with remaining cake; sprinkle with confectioners' sugar. Cut into squares. If desired, top with whipped topping and sliced bananas. Refrigerate leftovers.