Step 1

Preheat oven to 350 degrees. Line a 12 cup standard size muffin pan with cupcake liners.

Step 2

In a medium mixing bowl whisk together flour, baking powder and salt. Set aside.

Step 3

In a large mixing bowl using an electric hand mixer (or in the bowl of an electric stand mixer using a paddle attachment), blend together butter and granulated sugar on low speed until combined. Then whip until pale and fluffy on high speed, about 3 minutes. Scrape down bowl.

Step 4

Blend in egg, then blend in egg yolks and vanilla extract. Scrape down bowl.

Step 5

Add 1/3 of the flour mixture and mix on low speed just until combined. Mix in milk.

Step 6

Add another 1/3 of the flour mixture and blend, followed by buttermilk and blend, then last 1/3 of the flour mixture and mix til just combined.

Step 7

Scrape down bowl and fold with a rubber spatula to ensure ingredients are evenly combined, then transfer about 1/2 of the dough (I separated out 12 oz) to a separate mixing bowl and fold the espresso powder in with that portion until its evenly blended (it may not mix in fully that's okay, it will dissolve in as it bakes).

Step 8

Scoop about 2 Tbsp of the plain vanilla batter into cupcake liners and spread it out even just a little. Then top with about 2 Tbsp of the espresso batter.

Step 9

Bake cupcakes in preheated oven until toothpick inserted into center comes out clean, about 18 to 22 minutes. Let cool in muffin pan for a few minutes then transfer to a wire rack to cool completely.

Step 10

In a large mixing bowl using an electric hand mixer blend mascarpone and powdered sugar until combined.

Step 11

Add heavy cream and whip on medium-low speed gradually increasing to high speed. Whip until medium stiff peaks form, then add vanilla and whip until very stiff peaks form.

Step 12

Pipe or spread frosting over cupcakes then dust with cocoa powder. Store cupcakes in the fridge.