Katie’s Texas Sheet Cake: Classic Cocoa Frosting

Katie’s Texas sheet cake is a thin, tender chocolate cake baked in a large rimmed pan and covered with warm cocoa frosting while the cake is still hot. Butter, cocoa, and a little buttermilk give it a rich flavor and soft crumb, while the quick-poured frosting sets into a smooth, slightly fudgy layer.

Ingredients

2 cups (250 g) all-purpose flour
2 cups (400 g) granulated sugar
1 teaspoon baking soda
½ teaspoon fine salt
1 cup (226 g) unsalted butter, cut into pieces
¼ cup (21 g) unsweetened natural cocoa powder
1 cup (240 ml) water
½ cup (120 ml) buttermilk, at room temperature
2 large eggs (about 100 g without shells), at room temperature
1 teaspoon vanilla extract
For the frosting: ½ cup (113 g) unsalted butter
¼ cup (21 g) unsweetened natural cocoa powder
6 tablespoons (90 ml) milk
3½ cups (420 g) powdered sugar, sifted if lumpy
1 teaspoon vanilla extract
½ cup (60 g) chopped pecans, optional

Instructions

Heat the oven to 350°F (175°C). Grease a 13-by-18-inch (33-by-46-cm) rimmed sheet pan. A pan close to this size gives the cake its characteristic thin layers; do not use a flat cookie sheet without sides.
Whisk the flour, granulated sugar, baking soda, and salt together in a large bowl. In a medium saucepan, combine the 1 cup butter, ¼ cup cocoa, and water. Warm over medium heat, stirring, until the butter melts and the mixture just reaches a boil. Pour it over the flour mixture and whisk until no dry patches remain.
In a small bowl, whisk the buttermilk, eggs, and 1 teaspoon vanilla. Gradually whisk this into the chocolate batter until smooth. The batter will be fairly thin. Pour it into the prepared pan and spread it evenly into the corners.
Bake for 18–22 minutes, checking at 18 minutes. The cake is ready when the center springs back lightly when touched and a toothpick inserted in the middle comes out with a few moist crumbs but no wet batter. Avoid waiting for the toothpick to look completely dry, which can mean the thin cake has overbaked.
Make the frosting during the last few minutes of baking. In a saucepan, combine ½ cup butter, ¼ cup cocoa, and the milk. Heat, stirring, until the butter melts and the mixture just comes to a boil; take it off the heat. Whisk in the powdered sugar a cup at a time, then add the vanilla and pecans if using. Work promptly: the frosting thickens as it cools.
As soon as the cake comes out of the oven, pour the warm frosting over the hot surface. Spread it gently to the edges with an offset spatula or the back of a spoon. Let the cake cool in the pan until the frosting is set, about 30–45 minutes, then cut into squares.

Tips

Measure flour by spooning it into the measuring cup and leveling the top, or weigh it. Packing flour into a cup can make the cake dry and dense.
Buttermilk helps tenderize the crumb. If you do not have it, stir 1½ teaspoons lemon juice or white vinegar into ½ cup (120 ml) milk and let it stand for 5 minutes. The substitute works well, though the flavor may be a little less tangy.
Use natural, unsweetened cocoa rather than sweetened hot chocolate mix. Dutch-process cocoa can work, but natural cocoa’s acidity pairs more predictably with the baking soda in this version.
Pour the frosting while both cake and frosting are warm. If it cools and becomes too thick, briefly warm it over low heat and stir; do not add lots of extra milk, which can leave the topping runny.

Serving Suggestions

Serve the cake in small squares at room temperature, when the frosting is firm but the crumb remains soft. It is rich enough to serve on its own; for a plated dessert, add a scoop of vanilla ice cream or a spoonful of lightly sweetened whipped cream. Fresh strawberries or raspberries make a bright contrast to the cocoa. For a crowd, cut smaller pieces because the thin cake and generous frosting are satisfying.

Variations

For a nut-free cake, simply leave out the pecans; the frosting sets properly without them. For a deeper chocolate note, add ½ teaspoon instant espresso powder to the cocoa mixture, which emphasizes chocolate without making the cake taste strongly of coffee. You can also add ½ teaspoon ground cinnamon to the dry ingredients for a gentle warm spice. Some Texas sheet cake versions use different proportions, nuts, or frosting methods; this recipe keeps the classic thin, buttery cake and warm poured topping.

Storage and Reheating

Keep the cake covered in its pan or transfer pieces to an airtight container. Because the frosting contains milk, refrigerate leftovers within 2 hours of baking or serving. Store refrigerated for 3–4 days. The frosting firms in the refrigerator, so let a piece stand at room temperature for about 20–30 minutes before serving, or warm an individual slice briefly in the microwave until just softened. Avoid heating the whole pan, which can melt the frosting unevenly.

To freeze, cut the fully cooled cake into portions and freeze them in a single layer until firm, then wrap or place in a freezer-safe container for up to 2 months for best quality. Thaw overnight in the refrigerator, then let the pieces sit at room temperature before serving. Do not leave the cake out for longer than 2 hours at room temperature.

Frequently Asked Questions

What pan should I use for Texas sheet cake?
A 13-by-18-inch rimmed half-sheet pan is ideal for the thin cake and even frosting coverage. A 10-by-15-inch jelly-roll pan makes a thicker cake and may need extra baking time; begin checking around 20 minutes and continue until the center is set.

Can I make the cake ahead?
Yes. Bake and frost it up to a day ahead, cool completely, then cover and refrigerate. Allow time for the frosting to soften slightly before serving. For the freshest texture, avoid cutting it until you are ready to serve.

Why is the cake dry?
It may have been overbaked or made with too much flour. Check the center early, and remove the cake when it springs back and a toothpick shows moist crumbs rather than wet batter. Weighing flour is the most reliable way to avoid adding too much.

Can I make it without buttermilk?
Yes. Use the milk-and-lemon-juice or vinegar substitute in the Tips section. Plain yogurt thinned with a little milk can also work, but mix it until pourable and measure ½ cup (120 ml).

Can I bake it in a smaller pan?
A smaller pan makes the batter deeper, so the center takes longer to bake and the result is less like a traditional thin sheet cake. Use a rimmed pan with roughly the same surface area when possible, and never fill a pan so high that batter can overflow.

How do I keep the frosting smooth?
Sift powdered sugar if it has hard lumps, whisk it into the hot cocoa mixture gradually, and spread the frosting as soon as it is ready. A few small bubbles are normal; vigorous whisking after adding sugar can introduce more air.

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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes

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