Ama B's Creamed Onion Casserole

This is Ama B's recipe that she makes for Thanksgiving. It's delicious and easy. You can do it ahead and freeze it (without breadcrumbs) if you'd like.
Serves 6

Preheat oven to 350

2 lbs frozen pearl onions or fresh
6 tbl butter
1 onion, finely chopped
2 1/2 tbl flour
1/2 cup milk
1/2 cup cream
nutmeg
salt & pepper to taste
3/4 cup dry bread crumbs

If using fresh onions, boil for 1 minute, drain and cool. Trim and slip off skins. Cut an X 1/8" deep in root end of onions and simmer in water to cover for 15-20 minutes.

Remove onions from water & reduce liquid to 1 cup. Melt 2/3 of the butter in a saucepan and saute chopped onions over medium high heat for 7 minutes. Add flour and cook 2-3 minutes more, stirring. Add reserved cooking liquid, milk, and cream. Stirring constantly cook for 3-4 minutes until thickened. Season with salt, pepper, nutmeg. Add onions and simmer 3-4 minutes.

Place all in a buttered 2 quart baking dish and top with bread crumbs. Dot with remaining butter. Bake on top shelf of onion for 15-20 minutes.