Old Fashioned Texas Sheet Cake (with buttermilk)
A classic buttermilk cocoa powder cake, topped with cocoa frosting and walnuts. It starts with the old-fashioned technique of making a chocolate custard on the stovetop and uses mostly pantry ingredients. It's a great cake recipe for beginners and for feeding many.
Servings 12 squares
Ingredients
Chocolate cake:
- 1 cup unsalted butter
- 1 cup water
- ⅓ cup unsweetened cocoa powder I use Dutch-process cocoa powder
- 2 cups all-purpose flour
- 1 teaspoon baking soda
- ½ teaspoon salt
- ½ teaspoon ground cinnamon
- 2 cups granulated sugar
- 2 slightly beaten eggs at room temperature
- ½ cup buttermilk at room temperature
- 1 ½ teaspoons vanilla
Chocolate walnut frosting:
- ¼ cup butter or margarine
- 3 tablespoons unsweetened cocoa powder I use Dutch-process cocoa powder
- 3 tablespoons buttermilk
- 2 ¼ cups sifted powdered sugar
- ½ teaspoon vanilla
- ½ cup chopped walnuts
Instructions
- Preheat oven to 350°F (180°C). Grease a 10x15-inch cake pan; set aside.
Make the cake:
- In a medium saucepan, combine 1 cup unsalted butter, 1 cup water, and ⅓ cup unsweetened cocoa powder. Bring to a boil, stirring constantly. Remove from heat.
- In a large mixing bowl, sift together 2 cups all-purpose flour, 1 teaspoon baking soda, ½ teaspoon salt, and ½ teaspoon ground cinnamon. Add 2 cups granulated sugar and stir to incorporate.
- Add 2 slightly beaten eggs, ½ cup buttermilk, and 1 ½ teaspoons vanilla to the dry the ingredients. Beat with an electric mixer on low to medium speed to combine.
- Add the cocoa mixture and beat until well blended, but don’t overmix. Pour batter into the prepared pan.
- Bake for about 20-25 minutes or until the cake springs back when lightly touched and a cake tester or toothpick comes out clean. Sometimes it can take a few more minutes, so adjust the time to your oven. Don’t overbake it. If using a half-sheet cake pan, the time will be less and vice versa if using a 9x13-inch pan.
- Remove from the oven, place the pan on a wire rack and poke the surface with a brochette stick or toothpick. This can be optional, but the icing seeps a little into the cake and makes it moister.
- Immediately pour hot chocolate frosting (below) over the warm cake and carefully spread it to cover the entire cake as evenly as possible.
- Completely cool the cake in the pan before cutting it into squares.
- Store leftovers, well covered to avoid dryness, at room temperature for 3 days, a week in the fridge or a month in the freezer. Eat at room temperature.
Make the chocolate frosting:
- In a medium saucepan, stir together ¼ cup butter or margarine, 3 tablespoons unsweetened cocoa powder and 3 tablespoons buttermilk.
- Cook over medium heat, stirring until it breaks into a boil; remove from heat.
- Beat in 2 ¼ cups sifted powdered sugar, sifted for easier mixing, and ½ teaspoon vanilla with an electric mixer at low speed until blended.
- Stir in ½ cup chopped walnuts and mix to incorporate.
Notes
Cake pans you can use: A 10x15-inch pan, like I used today, is more in sync with the classic rimmed half-sheet pan (13x18 inches) or jelly roll pan (10x15 inches). You can also use a 9x13-inch pan, and the thickness of the cake will vary, of course.
You can make homemade buttermilk in a pinch: add a tablespoon of white vinegar or lemon juice per cup of whole milk and let it sit for five minutes before using. It will curdle slightly.
Toasted walnuts: This is not a required step, but it enhances the flavor. About 15 minutes in a medium oven until fragrant; be careful not to burn them! Let them cool completely before using so they stay crunchy. You can also use pecans.
