3 four gratin Recipes

butter, leeks (white and pale green parts only), sliced, onions , cut into eighths, shallots, halved, garlic cloves, minced, frozen baby onions, thawed, drained, whipping cream, dry breadcrumbs, chopped fresh parsley

red baby potatoes, thinly sliced, knorr four cheese pasta sauce mix , such as knorr brand, buttermilk, chopped chives, divided, dijon mustard , to taste