Heat the oven to 450°F with a rack in the top position. Lightly crumple a long sheet of aluminum foil. Uncrumple the foil and use it to line a small baking sheet. The little crumples will help keep the oysters upright as they cook.

Melt the butter in a small saucepan over low heat. Remove from the heat, stir in the lemon juice and Worcestershire sauce, and set aside for a minute.

Stir the cracker crumbs, green onions, parsley, and dry mustard together in a large bowl. Pour the seasoned melted butter into the crumb mixture and stir until the crumbs are evenly buttered.

Make sure the oysters are nestled comfortably in their half­shells. Top the oysters with the crumbs, dividing them evenly and tamping the topping down very lightly. Set the filled shells on the foil, wiggling them a little into the crumples to keep them steady.

Bake until the oysters are cooked and the tops are browned, about 12 minutes. Let stand for about 3 minutes before serving.

Note: If you don't have access to unshucked oysters or shells, bake these in ramekins or in muffin tins.