Description
An easy, one-bowl chocolate sheet cake that is incredibly moist thanks to buttermilk and boiling water, topped with a rich, no-bake fudge icing that creates a crackly shell.
Ingredients
Scale
- 2 cups (250g) all-purpose flour
- 1 ½ cups (300g) granulated white sugar
- ¾ cup (75g) unsweetened cocoa powder (Dutch-processed preferred)
- 1 ½ teaspoons baking soda
- 1 teaspoon baking powder
- 1 teaspoon salt
- 1 cup (240ml) buttermilk
- ½ cup (120ml) vegetable oil
- 2 large eggs, room temperature
- 2 teaspoons vanilla extract
- 1 cup (240ml) boiling water
- ½ cup (115g) unsalted butter (for icing)
- ½ cup (50g) unsweetened cocoa powder (for icing)
- 3 cups (360g) powdered sugar, sifted (for icing)
- 3–4 tablespoons whole milk (for icing)
- 1 teaspoon vanilla extract (for icing)
- ¼ teaspoon salt (for icing)
Instructions
- Preheat oven to 350°F (175°C). Grease a 9×13-inch baking dish with butter or non-stick spray, optionally dusting with cocoa powder.
- In a large mixing bowl, whisk together the flour, sugar, cocoa powder, baking soda, baking powder, and salt until no lumps remain.
- Add the buttermilk, vegetable oil, eggs, and 2 teaspoons vanilla extract to the dry ingredients. Beat on medium speed or stir vigorously for about 2 minutes until smooth and thick.
- Stir in the boiling water by hand. The batter will become thin and watery; this is normal. Pour evenly into the prepared baking dish.
- Bake for 30-35 minutes, or until a wooden toothpick inserted into the center comes out clean or with moist crumbs. Do not overbake.
- Remove from oven and let cool in the pan for 10 minutes. The cake should be warm, not hot, when icing.
- While the cake cools, make the icing: In a medium saucepan over medium heat, combine butter, ½ cup cocoa powder, and milk. Bring to a boil, stirring constantly.
- Remove saucepan from heat. Stir in powdered sugar, 1 teaspoon vanilla extract, and ¼ teaspoon salt until smooth and glossy.
- Pour the warm fudge icing over the slightly cooled cake. Spread evenly to the edges.
- Let the cake cool completely (about 30 minutes) before slicing to allow the icing to set into a crackly shell.
Notes
The boiling water blooms the cocoa powder for intense flavor and moisture. The cake must be warm when the icing is poured to allow it to soak in and set properly. If you don’t have buttermilk, make a substitute by adding 1 tablespoon of vinegar or lemon juice to 1 cup of milk and letting it sit for 5 minutes.
- Prep Time: 15 minutes
- Cook Time: 30 minutes
- Category: Dessert
- Cuisine: American
Nutrition
- Serving Size: 1 slice (1 of 12 sli
- Calories: 380
- Sugar: 38
- Sodium: 280
- Fat: 16
- Saturated Fat: 9
- Carbohydrates: 52
- Fiber: 2
- Protein: 4
Keywords: chocolate cake, buttermilk cake, sheet cake, fudge icing, easy dessert, moist chocolate cake, birthday cake, one-bowl cake