Preheat oven to 350°

Coarsely chop Mushrooms. Finely chop onion.

In large skillet cook sausage over medium heat. When sausage is halfway done add mushrooms and onions and cook until sausage is done. Season with garlic salt and pepper.

When cooked, turn off heat and add cream cheese to pan while pan is still hot. Stir until melted. Stir in mayonnaise and add two-thirds of the cheese.

Spread dip into an 9x9 glass pan. Top with remaining cheese and sprinkle Italian seasoning over cheese

Bake 18-22 minutes. Until mixture is bubbling.