Retro-Style Chocolate Sheet Cake: The Classic That Never Goes Out of Style
Classic thin-layer chocolate cake with tender, brownie-like texture topped with warm poured chocolate frosting. This nostalgic recipe feeds 24 people and uses simple ingredients. Perfect for potlucks, parties, and family gatherings. The cake bakes in just 20 minutes!
- Prep Time: 15 minutes
- Cook Time: 20 minutes
- Total Time: 2 hours 35 minutes (includes cooling)
- Yield: 24 servings
- Category: Dessert, Cake, Sheet Cake
- Method: Baking
- Cuisine: American
- Diet: Vegetarian
Ingredients
For the Cake:
- 2 cups all-purpose flour
- 2 cups granulated sugar
- 1 teaspoon baking soda
- ½ teaspoon salt
- 1 cup (2 sticks) unsalted butter
- 1 cup water
- ⅓ cup unsweetened cocoa powder
- 2 large eggs, room temperature
- ½ cup buttermilk, room temperature
- 1 teaspoon vanilla extract
For the Frosting:
- ½ cup (1 stick) unsalted butter
- ⅓ cup milk
- ⅓ cup unsweetened cocoa powder
- 1 pound (3¾ cups) powdered sugar, sifted
- 1 teaspoon vanilla extract
- Pinch of salt
Instructions
- Preheat and prep: Preheat oven to 350°F. Grease a 13×18-inch half-sheet pan or line with parchment paper.
- Mix dry ingredients: In a large bowl, whisk together flour, sugar, baking soda, and salt. Make a well in the center.
- Make chocolate mixture: In a saucepan, combine butter, water, and cocoa powder. Bring to a full boil over medium heat, whisking constantly. Remove from heat.
- Combine: Pour hot chocolate mixture into the well in dry ingredients. Stir until just combined. In a separate bowl, whisk together eggs, buttermilk, and vanilla. Add to chocolate batter and stir until smooth.
- Bake: Pour batter into prepared pan, spreading evenly. Bake 18-22 minutes until a toothpick inserted in center comes out with moist crumbs. Don’t overbake!
- Make frosting: About 5 minutes before cake is done, combine butter, milk, and cocoa in a saucepan. Bring to a boil, stirring constantly. Remove from heat and whisk in powdered sugar, vanilla, and salt until smooth.
- Frost warm cake: Immediately pour warm frosting over hot cake. Spread evenly to edges. Sprinkle with nuts if desired.
- Cool completely: Let cake cool completely in pan (at least 2 hours) before cutting into 24 pieces.
Notes
- Must use a 13×18-inch half-sheet pan for proper results (9×13 changes baking time significantly)
- Boiling the chocolate mixture is essential—don’t just melt
- Frost the cake while both cake and frosting are warm for authentic texture
- Make buttermilk substitute: ½ cup milk + 1½ tsp lemon juice
- Cake tastes even better the next day as flavors meld
- Add 1 tsp instant espresso powder to intensify chocolate flavor
- Traditional to sprinkle chopped pecans on wet frosting