Brown the pork sausage with sliced mushrooms, chopped onion, and chopped celery in a skillet over medium heat.

Drain off any excess grease.

Transfer the sausage mixture to a greased 9 1/2-10 inch pie plate or an 8x8 or 11x7 inch baking pan.

Mix in the diced cooked chicken and shredded Monterey Jack cheese.

In a separate bowl, beat the eggs, heavy cream, salt, pepper, and minced fresh parsley (if using) together.

Pour the egg mixture evenly over the meat and cheese mixture in the pie plate or baking pan.

Bake in a preheated oven at 350°F (175°C) for 35-40 minutes, or until the center is set and the top is nicely browned.

Remove from the oven and let stand for 10 minutes before cutting and serving.