I used a 1M tip to make the swirls. The swirls stick better if you spread a thin layer of frosting onto the cake first.
2C all-purpose flour
1 tsp baking soda
1C butter, room temperature
¼ C cocoa powder
2 eggs, lightly beaten
1 tsp vanilla extract
for peanut butter frosting
½C butter, room temperature
1C creamy peanut butter
3 tbs milk
2C powdered sugar
- for cake: Preheat oven to 350°.
- Grease and flour a round or square pan (I used a 9" spring form pan because it's what I had around).
- In a large bowl or stand mixer, combine flour, sugar, and baking soda.
- Melt butter in a heavy saucepan.
- Stir in cocoa.
- Whisk in water, buttermilk, and eggs; stirring well.
- Cook over medium heat, stirring constantly until the mixture boils.
- Add to flour mixture, stirring until smooth.
- Stir in vanilla extract.
- Pour batter into pan.
- Bake for 20-25 minutes or until a toothpick inserted comes out clean.
- Cool for 10 minutes on a wire rack.
- Cool completely before frosting.
- for peanut butter frosting: In a large bowl or stand mixet, beat butter and peanut butter until smooth.
- Gradually on low, add in powdered sugar.
- When mixture starts to thicken, add milk one tablespoon at a time.
- Beat on medium-high for at least 3 minutes until the frosting is smooth and fluffy.
- Spread a thin layer of frosting on the cake.
- Pipe on swirls using a bag fitted with a 1M tip. (Or just spread frosting all over the whole cake).