These chocolate and vanilla marble cupcakes are insanely delicious! Between the chocolate buttercream and the marbled cupcake, you will be licking your fingers clean!
Preheat the oven to 325°F. Line two muffin pans with cupcake liners and set aside.
Chocolate Batter
In a large bowl, whisk together the vegetable oil, warm coffee, egg, and vanilla until combined.
In a medium bowl sift together the flour, sugar, cocoa powder, baking powder, baking soda and salt. Add the dry ingredients to the wet and gently whisk until combined.
Vanilla Batter
In a large bowl, whisk together the flour, sugar, baking powder, baking soda and salt.
Add the buttermilk, milk, vanilla, and oil to the dry ingredients and whisk until fully combined. In a separate bowl whip, the egg whites until you get medium-stiff peaks and then gently fold the egg whites into the batter.
Use a small cookie scoop to alternate the chocolate and vanilla batter in the cupcake liners until they are 2/3 of the way full. Use a toothpick to swirl each liner once.
Bake for 18-20 minutes, until the centers of the cupcakes spring back when lightly pressed or a toothpick comes out clean from the center.
Remove from the oven and let cool completely before frosting.
Chocolate Buttercream
Beat the butter in the bowl of a mixer until fluffy and pale. Add the powdered sugar and beat slowly until incorporated, increasing the speed to beat it more fully.
Scrape down the sides and bottom of the bowl. Add the cocoa powder, milk, vanilla, and salt. Mix on medium-high until completely smooth and combined. If the frosting is too stiff, add more milk one tablespoon at a time until it is a pipeable consistency.
Pipe the frosting on top of the cooled cupcakes with either a round or star tip. Enjoy!