Cook onions slowly in bacon drippings until they begin to wilt, then add meat and sear.
Butter a large Pyrex dish and mix all ingredients except sour cream.
Cover with foil and bake at 325° for 1 hour.
At mid-point of cooking, stir gently but completely.
When done, stir lightly, dish up and place generous portion of sour cream on each serving.
Better still, let each guest add their own sour cream.
If some is left over, add a little water when reheating