Preheat the oven broiler and grease a baking dish.
In a bowl, mix the parmesan cheese, butter, mayonnaise, lemon juice, green onions, salt, and hot pepper sauce.
Arrange the halibut fillets in the prepared baking dish.
Broil halibut filets 8 minutes in the prepared oven, or until easily flaked with a fork. Spread the parmesan cheese mixture on top of filets, and continue broiling 2 minutes, or until topping is bubbly and lightly browned.