High Altitude Denver Chocolate Sheet Cake
An easy recipe for a moist and chocolatey Denver sheet cake, with fudgy icing and chopped walnuts.
All recipes on Curly Girl Kitchen are developed for high altitude at 5,280 feet. See FAQs for adjusting to higher or lower elevations.
Equipment
- 13x18 Rimmed Baking Sheet
Ingredients
Cake
- 1 cup buttermilk room temperature
- ½ cup unsalted butter, melted
- ½ cup vegetable oil
- 2 large eggs, room temperature
- 1 tbsp vanilla extract
- 1 ½ cups very hot water
- 2 ¼ cups all-purpose flour, fluffed, spooned and leveled
- 1 ¾ cups granulated sugar
- ½ cup unsweetened Dutch processed cocoa powder
- 1 tsp baking soda
- ½ tsp coarse Kosher salt (if using table salt, use half the amount)
Icing
- ½ cup unsalted butter, melted
- ¼ cup whole milk
- ¼ cup unsweetened Dutch processed cocoa powder
- 1 tsp vanilla extract
- 2 - 2 ½ cups powdered sugar
- ½ cup walnuts, chopped
Instructions
Cake
- Preheat the oven to 350 F, and position a rack in the center of the oven. Lightly spray a 13x18 inch rimmed baking sheet with non-stick baking spray, or line with parchment paper.
- In a large bowl, whisk together the buttermilk, melted butter, oil, eggs and vanilla. Very slowly, add the hot water to gradually temper the eggs so as not to scramble them, whisking until well combined.
- In a separate bowl, sift together the flour, sugar, cocoa powder, baking soda and salt. Add the dry ingredients to the wet, whisking for 10-15 seconds until combined. The batter will be thin.
- Pour the batter into the prepared pan. Bake the cake for about 25 minutes, until the top springs back when gently touched.
- Set the pan on a cooling rack, and make the icing.
Icing
- In a saucepan, heat the butter and milk over medium heat, until the butter is melted. Whisk in the cocoa powder and vanilla, then remove from the heat.
- Gradually add the powdered sugar, whisking the icing vigorously until smooth. If there are still lumps of powdered sugar that you can't whisk out, you can beat the icing for about 30 seconds with an electric mixer.
- Immediately, spread the icing over the hot cake, then sprinkle with the chopped walnuts. The icing will crust over quickly.
- Let the cake cool completely for several hours before cutting into 24 squares.
Notes
Store leftover cake in an airtight container at room temperature for up to 3 days.
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