Perch with Mushroom Sauce & Lemon

In a large skillet, saute 3 cups sliced fresh mushrooms, 4-6 
scallions chopped and 1/4 cup butter  until tender. Blend in 
2 T butter, 1 T chopped parsley, 1 tsp. salt, 1 tsp. grated 
lemon peel, 1/8 tsp. pepper and 1 cup milk, heat to boiling. 
Add 2 lb. perch fillets, spooning sauce over fish. Simmer 
covered over low heat, 15 min. until fish flakes easily. 
Remove fish to platter, stir sauce until smooth and pour 
over fillets. Serves 6.