For the cake:

2 cups sugar
1 stick unsalted butter, cut into pieces
1 vanilla bean, cut in half and seeds removed
2 eggs
3/4 cup unsweetened cocoa powder
1 cup brewed coffee
2 cups cake flour
2 teaspoons baking soda
1 teaspoon salt
1 tsp baking powder
1 cup milk

For the frosting:

1/2 cup peanut butter (not the crunchy or all-natural kind)
1/2 stick unsalted butter, cut into pieces, softened
1 egg yolk
1/2 cup confectioners' sugar
1/2 cup heavy cream
2 cups confectioners' sugar, sifted
Reese’s Peanut Butter Cups, mini size, roughly chopped