Preheat the oven to 350.
Mix Parmesan cheese, butter, mayonnaise, lemon juice, green onions, salt, and hot pepper sauce.
Arrange the halibut fillets in a greased baking dish.
Cook halibut fillets 8 minutes or until easily flaked with a fork.
Spread with the Parmesan cheese mixture, and continue cooking 2 more minutes or until topping is bubbly and lightly browned.