For topping: reeses peanut butter cups or buckeyes
Preheat oven to 325°F. Line cupcake liners in 2 muffin pans.
In a large bowl, combine the cake mix and chocolate pudding with a wooden spoon. Add the chocolate chips in now if desired (this will prevent them from sinking) and stir until combined. Next mix in the eggs, canola oil and water. Then stir in the sour cream and mix just until combined.
Pour cupcake mixture into the liners (about 3/4 the way full). Bake for 20-25 minutes or until a toothpick comes clean. Allow to cool on cooling rack.
Peanut Butter Frosting
In a large mixing bowl, combine the butter and peanut butter in a large bowl and mix with an electric mixer until smooth and fluffy.
Slowly mix in the powdered sugar and vanilla. Add in more heavy cream as needed to thin it out. You can also add more powdered sugar if needed to thicken. Mix until the frosting is smooth and creamy and you’ve reached your desired consistency. Taste and add more peanut butter if you'd like. If you are piping the frosting, it should be fairly thick.
Once cooled, frost your cupcakes using a 1M frosting tip.
Storage: Cover frosting tightly with plastic wrap and store in the refrigerator up to 1 week. Frosting: See my tips for how to frost a cupcake.