*To store: Baked, unfrosted cupcakes will keep up to 3 days in the fridge, after which I would decorate and serve within 2 days. Finished cupcakes, then, will keep for up to 5 days.
*Peanut butter: I suggest buying a non-natural peanut butter for the best texture in the cupcake filling and the buttercream. Or, if you do get the natural type, the kind that still contains palm oil or similar and doesn't separate. I like
Jif the best.