Preheat oven to 350° F. Line 12 muffin tins with muffin liners. Set aside.

In a heatproof bowl, place cocoa powder and boiling water together, whisking until a smooth paste forms.

In a medium bowl, whisk the flour, baking soda, baking powder, and salt. Set aside.

In the bowl of electric mixer using the paddle attachment, cream the butter with the sugar on medium-high speed until the mixture is somewhat light and fluffy.

On low speed, add 1/2 of the flour mixture and blend well. Add all of the cocoa mixture and again blend well.

On low speed, add the remaining dry ingredients. Mix only until the ingredients are well combined.

Carefully fill the muffin tins a little over 1/2 full using an ice cream scoop and bake for 20-22 minutes or until the cupcakes pull away from the sides of the muffin tins and a small sharp knife inserted into the center of a cupcake comes out clean. Allow to cool.

In the bowl of an electric mixer using the paddle attachment, blend together the butter and peanut butter.

On low speed add the confectioners' sugar and blend until smooth and fluffy. Set aside.

In a medium saucepan, bring the cream to a boil. Remove from the heat and add in the chocolate chips. Whisk the mixture until well blended and all the chips have melted. Mixture should be smooth. Pour ganache into a heat-proof bowl and set over an ice water bath, whisking constantly until the ganache thickens enough to be piped. Do not allow it to thicken too much.

Using a large, plain pastry tip, use the wider bottom opening and gently insert it into the center of each cupcake. Without going all the way to the bottom of the cupcake, twist the tip and pull out, removing a portion of the center of the cake. Save removed cupcake cores for snacking. If needed, use a small sharp knife to neaten the hole.

Using a pastry bag fitted with a large plain tip, fill the bag with peanut butter filling.

Push the top of the pastry tip into the hole you previously made in the top of each cup cake and squeeze some filling into the inside. Fill until the peanut butter is level with the top of the cupcake.

Fill another large pastry bag fitted with a large star tip with ganache. Decorate the top of each cupcake with swirls of ganache.

If desired, top with half of a peanut butter cup.