Peel and slice the onions. Fry in butter until golden brown. Beat the eggs and cream together, season, and add to onions. Line a deep pie plate with pastry. Pour in the onions and cover with pastry. Bake in a 350 degree F oven for 1 hour. The crust should be golden brown. For a change, crumbled crisp bacon or slivers of cheese may be put into the pie.