Sauté onions and philly meat in a pan until almost cooked, add in mushrooms and reduce as much water out of the pan before pouring into casserole dish to cool.
In food processor combine all ingredients of egg mixture until smooth
Lay 6 slices of cheese over the philly meat then pour egg mixture evenly around the casserole dish. Top with tomatoes
Bake for 30-35 min at 360 degrees until fully cooked
Cool for 15-20 minutes before slicing. This will allow you to cut it evenly and not burn your tongue off when you bite into it!!