Arrange fish fillets in a single layer over a baking sheet on a baking dish, fillets shouldn’t be packed closely together. Drizzle salt and pepper on both sides.
Combine butter, cream, garlic, lemon juice, mustard, salt, and pepper in a microwave bowl. Set for 2x30 sec bursts, stir in between until mixture is melted and smooth.
Toss the finely chopped shallots over fish fillets and pour sauce.
Bake for 10 to 15 minutes. If meat easily flakes with a fork, fish is cooked.