Using 1 TB of the Butter generously grease your pie plate
Melt remaking 4 TB Butter in large skillet and add Onions and cook for 2-3 minutes
Add Diced Mushrooms and Cook for 3 minutes
Add Zucchini and Corn Kernals, Spices and Salt and Pepper and cook for 8 Minutes then cool completely
In a large Mixing Bowl add both Shredded Cheeses, Eggs and Mustard and Stir
Add cooled veggies to the Cheese Mixture and pour into prepared Pie Plate and top with Parm Cheese. Cook in a preheated oven at 375 degrees for 35-40 minutes