Ingredients:

  • 2 cups (250g) all-purpose flour
  • 2 cups (400g) granulated sugar
  • 1/4 teaspoon salt
  • 1/2 cup (approximately 45g) unsweetened cocoa powder
  • 1 cup (240ml) water
  • 1 cup (2 sticks/227g) unsalted butter
  • 1/2 cup (120ml) vegetable oil
  • 2 large eggs
  • 1/2 cup (120ml) buttermilk
  • 1 teaspoon baking soda
  • 1 teaspoon vanilla extract
  • 1 cup (2 sticks/227g) unsalted butter
  • 1/4 cup (approximately 22g) unsweetened cocoa powder
  • 6 tablespoons (90ml) milk
  • 4 cups (480g) powdered sugar, sifted
  • 1 teaspoon vanilla extract
  • 1 cup (170g) chopped pecans or walnuts (optional)

Instructions:

  1. Preheat oven to 350°F (175°C). Grease and flour a 13x18 inch sheet pan.
  2. In a large bowl, whisk together flour, sugar, salt, and cocoa powder.
  3. In a medium saucepan, combine water, butter, and oil. Bring to a boil over medium heat, stirring until butter is melted.
  4. Pour the hot butter mixture over the dry ingredients and stir until combined. The batter will be thin.
  5. In a small bowl, whisk together eggs, buttermilk, baking soda, and vanilla. Add to the batter and mix until just combined. Do not overmix.
  6. Pour batter into prepared pan and bake for 20-25 minutes, or until a toothpick inserted in the center comes out clean.
  7. While the cake is baking, prepare the frosting. In the same saucepan (no need to wash it!), melt butter. Stir in cocoa powder and milk. Bring to a boil, stirring constantly.
  8. Remove from heat and add powdered sugar and vanilla extract. Beat with a whisk until smooth. Stir in nuts (if using).
  9. Immediately pour frosting over the hot cake. Spread evenly.
  10. Let the cake cool completely before cutting into squares.