Ingredients
| For the Cake | |
|---|---|
| 2½ cups all-purpose flour | plus extra for dusting the pan |
| 2 cups granulated sugar | |
| 1 tsp baking soda | |
| ¼ tsp salt | |
| 2 sticks unsalted butter | cubed, plus extra for greasing |
| ½ cup Dutch cocoa powder | sifted |
| 1½ cups water | |
| ½ cup buttermilk | |
| 2 eggs | lightly beaten |
| 1½ tsp vanilla extract |
| For the Frosting | |
|---|---|
| 1 stick unsalted butter | |
| ½ cup Dutch cocoa powder | sifted |
| 6 tbsp buttermilk | |
| 1 tsp vanilla extract | |
| ¼ tsp salt | |
| 3½ cups powdered sugar | |
| ½ cup chopped walnuts or pecans | optional |
Instructions
Make the Cake
- Preheat oven to 350°F (175°C). Grease and flour a 9″x13″ cake pan.
- In a large bowl, whisk together flour, sugar, baking soda, and salt. Set aside.
- In a small saucepan, combine butter, cocoa powder, and water. Heat over medium-low, whisking until butter melts and mixture is smooth.
- Pour cocoa mixture into dry ingredients and stir until just combined
- Add buttermilk, eggs, and vanilla. Mix gently until batter is smooth.
- Pour into prepared pan and bake for 28–32 minutes, or until a toothpick inserted in the center comes out clean.
- Let cake cool completely in the pan.
Make the Frosting
- In a small saucepan, melt butter over medium-low heat.
- Add cocoa powder and buttermilk, whisking constantly for 1 minute until mixture resembles thin pudding.
- Remove from heat and stir in vanilla, salt, and powdered sugar until smooth.
- Immediately pour warm frosting over cooled cake and spread evenly.
- Sprinkle with chopped nuts if desired.
- Let frosting set for at least 1 hour before slicing into 15 squares
