• Preheat over to 350°.
• Line two cupcake pans with paper liners.

Filling:

• combine the powdered sugar, peanut butter, butter and vanilla in a bowl.
• Beat with an electric mixer on medium speed until well combined
• Roll the mixture into 1" balls (at least 24) and set aside on a baking sheet.

Cake:

• combine the flour, cocoa powder, baking soda and salt in a medium bowl; whisk together and set aside.
• In a liquid measuring cup, stir together the sour cream, milk and vanilla extract.
• In your Bosch or Kitchen Aid mixer, add the paddle attachment and combine butter and sugar. Beat on medium-high speed until light and fluffy (approx. 2 min.).
• Beat in the eggs, one at a time, scraping down the bowl as needed.
• With mixer on low speed, alternately add the dry ingredients and the sour cream mixture, beginning and ending with the dry ingredients. Mix just until incorporated. Don't overmix.
• Spoon a tablespoon or two of batter into the bottom of each cupcake liner.
• Place a ball of the peanut butter filling in each cupcake well, then top with the remaining batter so that all the cupcakes are filled.
• Bake at 350° for 18-22 min. or until a toothpick inserted in the center comes out clean.
• Allow to cool in the pan for 5-10 minutes, then transfer to a wire rack to cool completely.

Frosting:

• In a medium sized bowl add cream cheese, butter, peanut butter and blend until smooth with an electric mixer. Gradually add the powdered sugar until all is well blended. Then fold in the whipped topping.