CAKE

Pre-heat oven to 350 degrees and grease muffin tins or fill with cupcake liners

In the bowl of a stand mixer, using the paddle attachment or an electric mixer, beat sugar and eggs at medium speed until well blended.

Add butter and vanilla and mix until light and fluffy (about 2-3 minutes)

In a large bowl, whisk flour and baking powder together

On low speed, add the dry ingredients to the wet ingredients, alternating the flour mixture with 1 cup of milk until just combined

Place 1 cup of cake mix into a medium bowl, add the cocoa powder and 1 tbsp milk, and stir until combined.

Place paper liners into the muffin tins and fill each one about 1/2 of the way to the top with vanilla batter

Place a tablespoon of chocolate batter over top, filling just below the top of the muffin tin. If you add more, the batter will spill over the top.

Use a toothpick or a sharp knife to create a swirl by mixing the two batters.

Bake in the oven at 350 for 18-20 minutes or until a toothpick comes out clean.

Remove and allow to cool on a wire rack for 30 minutes

BUTTERCREAM FROSTING

In a stand mixer, cream the butter until it's smooth and fluffy

Slowly add 3 cups of powdered sugar and cocoa powder until it's mixed in and then beat on high for 2-3 minutes

Add in the vanilla and milk and continue beating until it's smooth, then add the remaining cup of sugar until creamy

Using a pastry tip or the edge of a knife, cut a 1" circle on the top of the cupcake. Make sure it's deep enough so you can fill it with marshallow.

Spoon marshmallow fluff into a piping bag or ziplock bag with the tip cut off and pipe the marshmallow into the opening of each cupcake.

Take the piece of cupcake you removed and push it back into the hole to seal the marshmallow inside.

Frost cupcakes and add sprinkles

Storage