Start the potatoes in cold water, add salt, and bring to a boil. Boil until a fork comes out easily. Use a fork and not a knife, it will give you a more accurate measure of if the potatoes are cooked through.

Drain the potatoes in a colander.

Put the warm potatoes through a food mill (or a ricer).

Add the butter, cream cheese, salt, pepper, and cream of tartar.

Add about half of the warm cream. Save the rest to get the right consistency. You can always add, but cannot take away, so it is better to start slow.

Whip until light and fluffy. Check for seasoning.

Spray a casserole dish (mine was 2 quarts) with cooking spray.

Spread the potato mixture into the casserole dish. At this point, you can cover it with plastic wrap and keep it in the fridge overnight.

If you are baking this straight away, bake at 350 degrees for 30 minutes. Put it under the broiler for a few seconds to crisp up the top. If you are taking this from the fridge, let it sit out at room temperature so that it is not ice cold, and then bake.