Extra peanut sauce can be refrigerated for a few days (it may harden a bit in the fridge, thaw before next application). (sharedappetite.com)
They will harden a bit on the outside as they cool but still be a bit soft and fluffy on the inside. (delightfulvegans.com)
Ideally I would make the cupcakes Friday night, freeze them overnight, then thaw them in the morning, decorate them, and store them in the fridge just for a few hours to let the frosting harden a bit before serving. (ericasweettooth.com)