Chocolate 20 Minute Cake (Sheet Cake)

Chocolate 20 minute cake is the Texas-style sheet cake everybody’s grandmother seems to have a recipe for. The genius is in the technique: butter, shortening, cocoa, and water boil together on the stovetop, then the hot mixture pours straight into the dry ingredients. The boiling liquid pre-blooms the cocoa and pre-cooks the flour slightly, giving you a tighter crumb that’s almost brownie-like.

The buttermilk is the move that makes this cake so tender. The acid in buttermilk reacts with the baking soda for lift, and the milk solids tenderize the flour proteins. You can swap regular milk plus a teaspoon of vinegar in a pinch.

The icing is the other half of what makes this cake legendary. Hot icing poured over warm cake means the icing soaks slightly into the top while the rest sets up into a glossy, slightly fudgy layer. Most cakes get cool frosting on cool cake, which gives a totally different texture. Don’t skip the timing.

A pound of powdered sugar in the icing sounds like a lot, but it’s necessary to balance the half cup of butter and four tablespoons of cocoa. Sift the sugar to avoid lumps that show up in the smooth-poured surface.

This cake is built for transport. Bake it in a sheet pan, ice it, cover with foil, and bring it. It travels well and slices clean.

Pro Tips

• Use a 13×18 inch jelly roll pan or 13×9 inch sheet pan. Smaller pans give thicker, less authentic cake.
• Pour icing on cake while both are still warm. Cold icing on cold cake gives a flatter, less glossy finish.
• Add ½ cup chopped pecans to the icing for the traditional Texas version.
• Cool completely before slicing for cleaner cuts.

Variations

• Add 1 teaspoon of cinnamon to the cake batter for Mexican chocolate spice.
• Stir 1 teaspoon espresso powder into the boiling cocoa mixture for deeper chocolate flavor.
• Use a buttercream frosting instead of the boiled icing for a fluffier, less dense top.