The cake batter is very simple. You make it like you're making vanilla cupcakes, and then put some to the side and add cocoa powder and milk. The frosting you have to make two separate frostings for, but still rather quick. The hardest part of this recipe is trying to as neatly as possible squeeze only vanilla frosting into one side of a piping bag and then only chocolate into the other, and then hope it pipes out well. I have to say I did a pretty good job for the first time, but if you give it a try and you end up needing several tries, don't feel bad, it's difficult. My advice would be to do it in two or three segments. Start with most of the bag folded down and do vanilla on one side and then chocolate on the other. Then bring up the folds and do the next segment, and that will probably be it because you don't want to over-fill the bag.
Marble Cupcakes with Vanilla and Chocolate Swirl Frosting
Cupcakes:
- 1⅔ cups all-purpose flour
- ½ tsp. baking powder
- ¼ tsp. baking soda
- ½ tsp. salt
- ½ cup butter, melted
- 1 cup granulated sugar
- 1 large egg
- ¼ cup sour cream
- ¾ cup + 1 Tbsp. milk, divided
- 2 tsp. vanilla extract
- ¼ cup cocoa powder
Chocolate Frosting:
- 1 ¾ cups confectioners’ sugar
- ¼ cup cocoa powder
- ½ cup butter, softened
- 2 Tbsp. milk
- ¼ tsp. salt
Vanilla Frosting:
- 1 ¾ cup confectioners’ sugar
- 1 tsp. vanilla extract
- 1-2 Tbsp. milk
- ¼ tsp. salt
- ½ cup butter, softened
Make the cupcakes: Preheat the oven to 350 degrees F. Line 14 muffin cups with paper liners and set aside. In a medium bowl, whisk together the flour, baking powder, baking soda, and salt; set aside. In a large bowl, add the melted butter and sugar and mix until no more sugar can be seen, it will be very thick. Add the egg, sour cream, ¾ cup milk, and vanilla extract and mix well. Add the flour mixture and mix until no more lumps are found. Transfer 1 cup of batter to another medium bowl and add the cocoa powder and 1 Tbsp. milk. Mix until smooth, it will be thick.
Spoon about 1½ tablespoons of vanilla batter into paper liners, then about 1 tablespoon of chocolate batter, then more vanilla, and continue until all the cupcake liners are about ¾ of the way full and all the batter is used up.
Bake for 20 – 24 minutes, or until a toothpick inserted in the center comes out clean. Cool in muffin tin for about 10 minutes before carefully removing to a wire rack to cool completely before frosting.
Make the chocolate frosting: Sift together the confectioners’ sugar and cocoa powder in a small bowl until no lumps remain. In the bowl of an electric mixer (or using a handheld mixer), cream the butter. Gradually add the flour mixture and then the milk and salt. Mix on high speed until fluffy; set aside.
Make the vanilla frosting: With a handheld or stand mixer, beat the butter until fluffy. Add the confectioners sugar and beat until combined. First add the vanilla extract and beat well. Add one tablespoon of milk and mix on high speed; add more milk very slowly to reach desired consistency. Add salt and beat well.
Assemble the cupcakes: Fill a piping bag fitted with a large tip (I used open star, or 1M) halfway with vanilla frosting and halfway with chocolate frosting (vertically-wise, as in if you’re looking down at the piping bag from the top, one half should be vanilla and one half should be chocolate). It doesn’t need to be perfect, as best as you can do. Pipe the frosting as you usually would onto the cupcakes.