This wonderfully savory make-ahead vegetarian breakfast casserole is brimming with vegetables. It’s perfect to feed a crowd on Christmas morning or at a festive brunch. I like to use my 5-quart braiser for this dish, because it can go from stovetop to oven. If you don’t have one of those, you can do the stovetop part in a 12-inch skillet and the baking part in any 5-quart baking dish.