Cover the bottom of a 10-in. gratin with finely-crumbed saltines mixed with pepper, paprika, chopped shallots, and parsley. Add a layer of oysters that have been rolled in the crumb mixture, then top with another layer of crumbs and grated parmesan. Drizzle with only enough melted butter to moisten, then slowly pour heavy cream into the edge of the dish until oysters are just covered. Place in a very hot oven until bubbling and browned.