Preheat your oven to 350 degrees. Butter a 9x13 inch baking dish and set aside.
Bring a large pot of salted water to a boil.
Wash and dry the green beans. Place them on a large cutting board and trim off the ends, then cut the green beans in half.
Add the beans to the water and boil for 6 minutes, drain and place into the prepared baking dish.
Meanwhile, heat a large skillet over medium-high heat and add the butter.
When the butter is melted add the mushrooms and garlic. Stir and cook for 3-minutes until vegetables are tender.
Sprinkle the flour over the vegetables and stir for one minute.
Slowly stir in the chicken broth and milk until your sauce is smooth.
Season with salt, pepper, Italian seasoning, and Paprika then reduce heat to low and allow the sauce to come to a simmer.
Remove the pan from the heat and stir in the cheese until melted.
Pour the sauce over the green beans and stir in 1/2 cup of the french fried onions.
Bake for 15 minutes, until bubbly.
Remove the casserole from the oven and top with remaining onions, bake for 5 more minutes.