PREHEAT the oven to 350° F.
MELT the butter in a large pot on high heat and add in the onions and cook for 3 to 4 minutes.
ADD in the mushrooms and cook until they are lightly brown.
SPRINKLE the flour over top of the mushrooms and onions and stir until they are completely coated.
POUR in 3 cups of chicken stock and bring to a boil.
WHISK in the heavy cream.
ADD the sauce to a large pot with the parboiled green beans and mix together.
SEASON with salt and pepper and fold in the chopped bacon.
POUR the mixture into a Reynolds Kitchens® 13x9 Pasta & Casserole Pan with hot pad and carrier and sprinkle on the 2 cups of bread crumbs and then the 2 cups of French fried onions.
BAKE in the oven on 350° for 30 minutes or until the French fried onions and bread crumbs turn golden brown.