Mix bay leaf, wine, onion, water and salt with paprika (or pepper) in a Casserole Dish, add the rolled files, Cover and Microwave for 3 minutes at high power.
Arrange the fish in another casserole dish, throw away the bay and reserve the liquid (broth).
Melt the butter and add the flour, keeping the heat low. Saute for about 2 minutes, stirring constantly.
Add the reserved broth (from the preparation) very gradually, stirring vigorously with a whisk, and let it come to a boil, often stirring to avoid scorching. When it comes to a boil, lower the heat and simmer for 1-2 minutes, continuing to stir. Taste the salt and pepper. I like to add Paprika.
Remove from heat, stir in the cream (whipping cream/thick cream/heavy cream/evaporated milk).
Pour the white sauce over the reserved fish on a casserole dish.
Sprinkle with grated Parmesan cheese and bake in a Conventional Oven until golden brown.
Serve with asparagus, Mashed potatoes, green salad, rice.