In a large pot, bring 6 cups of water to boil. Add green beans and cook 5 minutes. Once cooked, drain green beans into a colander and set aside.
Preheat oven to 375°F.
In a large skillet, heat olive oil over medium-high heat. Add onions and mushrooms and sauté for 5-7 minutes, or until soft. Sprinkle with flour, stir, and turn off heat.
In a large casserole dish, combine green beans, onion and mushroom mixture, chicken stock, salt, pepper, Worcestershire sauce, and milk.
Bake at 375°F for 15 minutes. Remove from oven and sprinkle with French fried onions and Parmesan cheese. Bake for an additional 5 minutes.
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