Cut fish into serving-sized pieces, if necessary.
In large skillet, place fish and pour sauterne over.
Bring to boil; reduce heat and simmer, covered, for about 5 minutes or until fish flakes easily with fork.
With slotted spoon, remove fish to serving platter and keep warm.
Strain and measure poaching liquid; return 1/3 cup (75 mL) liquid to skillet.
Blend cornstarch, salt and cream until smooth.
Stir into skillet; cook, stirring constantly, until mixture comes to boil and thickens.
Add grapes and heat through.
Spoon sauce over fish.