Denver Chocolate Sheet Cake

A rich, fudgy classic with roots in community cookbooks and timeless flavor.

This beloved chocolate sheet cake first made its mark when the Junior League began publishing cookbooks to raise funds. The Denver edition featured this standout recipe—and it’s easy to see why it became a favorite. There’s nothing fussy or overcomplicated here—just pure chocolate goodness in a soft, moist cake, topped with a silky cocoa frosting and optional crunchy nuts for a little extra flair.

🧾 Ingredients

👩‍🍳 Instructions

Make the Cake

1. Preheat oven to 350°F (175°C). Grease and flour a 9″x13″ cake pan.
2. In a large bowl, whisk together flour, sugar, baking soda, and salt. Set aside.
3. In a small saucepan, combine butter, cocoa powder, and water. Heat over medium-low, whisking until butter melts and mixture is smooth.
4. Pour cocoa mixture into dry ingredients and stir until just combined.
5. Add buttermilk, eggs, and vanilla. Mix gently until batter is smooth.
6. Pour into prepared pan and bake for 28–32 minutes, or until a toothpick inserted in the center comes out clean.
7. Let cake cool completely in the pan.

Make the Frosting

1. In a small saucepan, melt butter over medium-low heat.
2. Add cocoa powder and buttermilk, whisking constantly for 1 minute until mixture resembles thin pudding.
3. Remove from heat and stir in vanilla, salt, and powdered sugar until smooth.
4. Immediately pour warm frosting over cooled cake and spread evenly.
5. Sprinkle with chopped nuts if desired.
6. Let frosting set for at least 1 hour before slicing into 15 squares.