Preheat oven to 350 degrees. Spray a 10 X 13 casserole dish with nonstick cooking spray. Place 2 pounds of flounder fillets in baking dish. Combine1 cup of reduced fat sour cream (do not use fat free) with 1 tsp salt, 1 tbsp paprika, 1 to 2 tsp Tabasco sauce, and 1/4 cup of grated parmesan cheese. Mix until smooth. Spread sour cream sauce over the top of the fish. Top with 1/4 cup bread crumbs. Melt 3 tbsp of unsalted butter in the microwave. Pour the melted butter over the bread crumbs. Place in oven and bake for thirty minutes, or until fish is thoroughly cooked. (Test by making sure it flakes easily with a fork).