What do you do with your leftovers? When I was a kid, some nights my mother served a dish she called “round potatoes.” They were patties 4-5 inches wide, 3/4 inch thick, fried in a cast iron skillet. My brother and I loved them. It never occurred to us that we were eating leftovers, though now it’s clear these were recycled mashed potatoes. Ah, leftovers. Culinary alchemy makes gold of them.