Preheat oven to 350 degrees and line pans with cupcake liners (yields 22).
Peanut Butter Filling: Cream all ingredients until well combined and set aside.
Chocolate Cake: In a large bowl, combine eggs, oil and vanilla (do not over beat the eggs).
Add sour cream, yogurt and milk and stir well.
Add cake mix (for easy mixing sift cake mix into batter).
Fill cupcake liners ½-3/4 full.
Place about 1 ½ teaspoons peanut butter filling on top of batter. Then, do your best to push the filling down into the batter. (Unlike my photo where it is just sitting on top.) If you don’t push the filling into the middle, it may slide over while it bakes, that is what mine did.