Step 1

In a large pot of boiling water cook potatoes until tender, drain well.

Step 2

In a small frying pan add 1 tablespoon of butter and chopped onion sauté  until slightly golden.

Step 3

Pre heat oven to 350°.  Lightly butter a 10 x 7 inch baking dish (approximately).

Step 4

Place drained potatoes in a large bowl and mash with a potato masher, then add 3 tablespoons of butter and milk and beat until creamy.(If needed add a little more butter and or milk).  Fold in onion butter mixture and shredded mozzarella cheese.

Step 5

Spoon into prepared baking dish.  Top with Parmesan and chopped parsley.  Bake for approximately 10 - 15 minutes (I broiled it for the last 5 minutes to brown the top). Let sit a couple of minutes before serving.  Enjoy!