Recipe
Chocolate Sheet Cake with Colorful Frosting
A simple, moist chocolate cake decorated in the best way—with lots of delicious vanilla buttercream! The buttercream is piped in multiple colors and shapes, covering the entire cake for a festive look.
Time: 3 hours 
Difficulty: Moderate
Yield: 16 personerIngredients
Chocolate Cake:
- 200 g flour
- 100 g cocoa powder
- 1 tsp baking soda
- ¼ tsp salt
- 1 ½ dl vegetable oil
- 350 g sugar
- 1 ½ tsp vanilla
- 3 eggs
- 2 ½ dl buttermilk*
Vanilla Buttercream:
- 350 g butter (unsalted is best, room temperature)
- 450 g powdered sugar
- 1 tsp vanilla
- 2-3 tbsp heavy cream
Instructions
Chocolate Cake:
- Grease a baking pan, approximately 23 x 33 cm (9 x 13 inches).
- In a large bowl, mix flour, cocoa powder, baking soda, and salt.200 g flour, 100 g cocoa powder, 1 tsp baking soda, ¼ tsp salt
- In another bowl, whisk together oil, sugar, vanilla and eggs. Add buttermilk and mix well.1 ½ dl vegetable oil, 350 g sugar, 1 ½ tsp vanilla, 3 eggs, 2 ½ dl buttermilk*
- Gradually pour the wet ingredients into the flour mixture, stirring gently with a spatula or wooden spoon until combined. Be careful not to overmix.
- Bake at 180 °C (356 °F) for 28-30 minutes. The cake is done when a toothpick inserted in the center comes out clean.
- Let the cake cool completely in the pan on a wire rack.
Vanilla Buttercream:
- Place butter in a mixing bowl (or the bowl of a stand mixer) and beat on medium speed for about 5 minutes until fluffy.350 g butter
- Add powdered sugar and vanilla, mixing until combined.450 g powdered sugar, 1 tsp vanilla
- Slowly add heavy cream, one tablespoon at a time, until you reach the desired consistency.**2-3 tbsp heavy cream
- Divide the buttercream into separate bowls, one for each color you want to use. Color the buttercream with gel food coloring (add a little at a time, as gel colors are strong!). Cover the bowls with plastic wrap to prevent drying.
- Fill piping bags with different buttercream colors and pipe decorations onto the cake using various piping tips. Optionally, decorate with sprinkles or other edible decorations.
Notes
*If you don’t have buttermilk, you can substitute by mixing 2 tbsp lemon juice into regular milk and letting it sit for 10 minutes.
**For firmer buttercream, add more powdered sugar. For softer buttercream, add more heavy cream. The buttercream should hold its shape but still be soft enough to pipe without excessive pressure.
Storage: The decorated cake should be covered with plastic wrap and stored in a cool place. Avoid refrigeration unless storing overnight. If refrigerated, bring the cake to room temperature before serving so the buttercream softens.