This Creamed Onion Gratin is one of those timeless recipes that will always have a place at the Southern holiday table. If you've planned ahead, you already stored your surplus of spring Vidalia's to enjoy throughout the year. If not, any sweet onion will do. First, the onions are slowly caramelized to bring out (even more of) their ultra sweet flavor, and laced with sherry to add another dimension of taste. The tender onions are then tossed in a rich and creamy cheese sauce and topped with buttery panko crumbs. The results are baked into a bubbling golden brown casserole so good you'll want to eat it straight from the pan with a spoon.