Prepare Mushroom Stuffing.
Put butter in saucepan.
Add onion; saute until golden but not brown.
Add mushrooms; cook until water from mushrooms cooks away.
Remove from heat.
Add bread crumbs, chicken stock, egg, 1/2 teaspoon salt, and pepper; mix well with hands.
Clean and rub inside of fish with 1 teaspoon salt.
Stuff fish; fasten with toothpicks.
Place, underside down, in greased baking dish; layer bacon over fish.
Bake in 350Â°F oven 1 hour or until fish flakes easily.