for sauce: heat champagne, shallots, vinegar and peppercorns in a saucepan and boil until reduced to 1/4 cup, about 20 minutes, set aside. for marinade: combine champagne, oil, shallots, pepper and shrimp in a plastic bag and seal.
marinate for 30-60 minutes heat oven to broil remove shrimp to a broiler pan that's been sprayed with non-stick spray, discard marinade broil shrimp 2 minutes per side, remove. rewarm sauce over medium heat, adding butter in bits and whisking until melted before adding more.
season with salt and pepper if desired serve 4 shrimp per plate and spoon sauce around.