Possible Clues:

• Au _______
• Au . . . . . . - cooked with a crust of melted cheese
• Au . . . . . . means cooked with melted cheese
• Grated cheese or breadcrumbs on a dish
• Casserole crust
• Grinding nearly all of the cheese
• Au ___ (how some potatoes are served)
• Crust trapped vermin?
• Dish with corn -- time to tuck in
• 'Au ..., with a cheesy topping (6)'