These fun and festive marble cupcakes combine rich chocolate and vanilla batters in every bite. A swirl of each frosting on top makes them party-ready, but they’re easy enough for anytime baking.
Preheat the oven to 350°F (175°C). Line 12 muffin cups with paper liners.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.
Cream the butter and sugars in a large bowl until light and fluffy (2–3 minutes). Add the eggs one at a time, mixing well after each. Mix in the vanilla.
Add the flour mixture in three portions, alternating with the buttermilk and milk. Begin and end with the dry ingredients, mixing just until combined.
Transfer about half of the batter (about 1 1/2 cups) to a small bowl. Stir in the cocoa powder, melted chocolate, and espresso powder if using. If the mixture is too thick, add 1–2 teaspoons of milk to loosen. (It should have a similar consistency to the vanilla batter.)
Fill each cupcake liner with alternating spoonfuls of vanilla and chocolate batter. Use a skewer or knife to gently swirl the batters together.
Bake for 18–22 minutes, or until a toothpick inserted in the center comes out clean. Cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.
To make the vanilla buttercream:
Beat the butter until smooth. Add the confectioners’ sugar gradually, mixing well.
Add the milk, vanilla, and salt. Beat until fluffy. Add more sugar or milk as needed for piping consistency.
To make the chocolate buttercream:
Beat the butter until smooth. Sift together the sugar and cocoa powder, then add to the butter gradually.
Mix in the milk, vanilla, and salt. Beat until light and creamy. Adjust the texture as needed with sugar or milk.
To assemble:
Spoon each frosting into a small piping bag (one for each frosting).
Flatten each slightly, snip the ends as normal, then place on top of or beside each other in a large piping bag fitted with a large star tip (like Wilton 1M or 2D). Chill briefly if needed for easier piping.
Pipe the frosting onto the cooled cupcakes.
Video
Notes
Chocolate swirl: If the chocolate batter thickens too much after adding cocoa and melted chocolate, stir in 1–2 teaspoons of milk to loosen it up.
Two-tone frosting: For the best swirl, place each frosting in a small piping bag. Snip the tips and place both into a larger piping bag fitted with a star tip. For an even distribution of the frosting, make sure you’re pressing both frostings when piping, not just one. The spot where you naturally apply pressure should be over both frostings.
Make-ahead tip: The cupcakes can be baked a day ahead and stored in an airtight container up to 2 days. You can also freeze the unfrosted cupcakes for up to 3 months.
Frosting storage: Vanilla and chocolate buttercream can each be frozen in airtight containers for up to 3 months. Thaw in the fridge, bring to room temp, and re-whip before using.