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

Using a stand mixer or electric mixer, beat the butter and sugar on medium high speed for 4 minutes, until lightened in color and fluffy.

Add the egg and vanilla and beat until combined.

In a small bowl mix together the buttermilk and sour cream. In a separate small bowl mix together flour, cocoa powder, baking soda and salt.

To the butter/sugar mixture, add a third of the dry ingredients and mix until incorporated. Add half of the buttermilk/sour cream and mix well. Continue alternating the dry and wet ingredients ending with the dry ingredients until combined.

Scoop the batter into the cupcake pan dividing it evenly between the 12 cavities. Bake for 14-16 minutes until a cake tester/toothpick inserted into the middle of a cupcake comes out clean or with a few moist crumbs.

Let the cupcakes cool in the pan for about 5 minutes and then transfer to a wire rack to cool completely.

Place the chopped chocolate in a small bowl and set aside.

Heat the heavy cream in the microwave for 45 seconds.

Pour the hot cream over the chocolate and place a plate or plastic wrap over the bowl. Let it sit for about 1-2 minutes.

Remove the plastic wrap/plate and stir the cream and chocolate until the chocolate is completely melted and a thick ganache forms. Refrigerate for 30 minutes.

Beat the softened butter with the powdered sugar and cocoa powder on low speed and increasing to medium speed until combined.

Add heavy cream and the vanilla and mix until creamy. Add the melted chocolate and mix until combined.

Use a sharp paring knife or cupcake corer to create a hole in the middle of the cupcake (see pictures in post). Discard the cake that was cut out (or eat it!).

Using a spoon or small cookie scoop, scoop about 1-2 teaspoons of the ganache into each cupcake.

Frost the cupcakes using a knife or pipe the frosting using a bag and pastry tip.