Slow Cooker Green Bean Casserole

Steps

1. In a large saucepan melt 4 tablespoons unsalted butter over low heat. Whisk in 6 tablespoons flour and let cook for 1-2 minutes. Slowly stir in 1 cup chicken broth, then 1 cup milk. Whisk until it begins to thicken. Let it simmer for a few minutes. Season with 1 teaspoon salt and ½ teaspoon black pepper. Stir in 1/2 cup half and half, then set aside.
2. In a large non-stick skillet, sauté 8 ounces fresh mushrooms slowly so that they release all of their moisture. Season them with 1/2 teaspoon salt, 1/2 teaspoon black pepper, and 1/2 teaspoon ground thyme. When the mushrooms start to turn golden brown (after about 10 minutes), add them to the sauce from step 1. 
3. Stir in 1 cup finely grated parmesan cheese. 
4. In a large bowl, toss either fresh or frozen green beans with the mushroom sauce. Stir in bacon. Spray a slow cooker with non-stick cooking spray. Pour the green bean mixture into the slow cooker and sprinkle 1/2 cup French’s French Fried Onions over the top.
5. Fresh beans: cook on low for 4-6 hours Frozen beans: cook on low for 5-6 hours.
6. Shortly before serving, heat 1 tablespoon butter in a non-stick skillet over medium heat. Add in 1/2 cup panko bread crumbs and cook until lightly toasted. Add in 1 cup French Fried Onions and cook for a minute longer. 
7. When the green bean casserole is done cooking, transfer it to a serving dish. Sprinkle the french fried onion/panko bread crumb mixture over the top and serve.