Sprinkle fish with salt and pepper; fold in half. Place fish in 10-inch skillet;
add wine, water, shallots and lemon juice. Heat to boiling; reduce heat. Cover and
simmer until fish flakes easily with fork, 4 to 5 minutes.
Remove with slotted spatula to heatproof platter; keep warm.
Add grapes to liquid in skillet. Heat to boiling;
reduce heat. Simmer uncovered 3 minutes.
Remove grapes with slotted spoon.
Heat liquid in skillet to boiling; boil until reduced to 1 cup. Pour liquid into
measuring cup; reserve.
Heat 2 tablespoons butter in skillet until melted; stir
in flour. Cook and stir 1 minute; remove from heat.
Stir in reserved liquid and
whipping cream. Heat to boiling, stirring constantly. Boil and stir 1 minute.
Add 2 tablespoons butter; stir until melted.
Drain excess liquid from fish; spoon sauce
Heat oven to broil or 550 degrees F.
Broil fish 4 inches from heat just until sauce is glazed, about 3 minutes.