For the Peanut Butter Ball Filling:
2/3 cup confectioners' sugar
1/2 cup creamy peanut butter
2 tablespoons unsalted butter, softened
1/4 teaspoons vanilla extract

For Chocolate Cupcakes:
16 tablespoons (2 sticks) unsalted butter, cut into 8 pieces
4 ounces bittersweet chocolate, chopped
1 cup Dutch-processed cocoa powder
1 1/2 cups all-purpose flour
1 teaspoon baking soda
1 1/2 teaspoon baking powder
4 eggs
1 1/2 cup granulated sugar
2 teaspoon vanilla extract
1 teaspoon table salt
1 cup sour cream

For Peanut Butter Frosting:
2 cup confectioners’ sugar
2 cup creamy peanut butter
10 tablespoons unsalted butter, at room temperature
1 1/2 teaspoons vanilla extract
1/2 teaspoon kosher salt
2/3 cup heavy cream