I accidentally left a box of unsalted butter out overnight after going shopping. In the morning when I realized what I did, I promptly stuck the box in the fridge.
But would this butter be OK to use in an icing recipe? Or should I use it for cooking for my own family or throw it out?
It's fine for either. I worked in several bakeries where there was a butter cabinent. We'd put a case of butter in the cabinent and refill it every few days and leave it at room tempterature.