16 ounces frozen green beans
4 tablespoons butter
1/4 cup chopped white or yellow onion
2 cloves minced garlic
2 cups sliced mushrooms
2 tablespoons flour
1/4 cup chicken or vegetable broth
1 teaspoon Worcestershire sauce
1 cup sour cream
1/2 cup shredded cheddar cheese
1/4 cup heavy whipping cream or milk
1 large shallot, peeled and sliced thin (I subbed more white onion because I live in a town without shallots)
Preheat oven to 350F. Have a 1.5-2 quart casserole dish ready.
Bring a large pot of salted water to a boil. Boil green beans for 3 minutes. Drain and quickly run under cold water to stop the cooking. Let dry.
In a large deep skillet, melt 2 tablespoons butter. Add onions, garlic, and mushrooms and saute until onions start to brown and soften. Stir in flour and cook 1 minute. Stir in the broth and Worcestershire sauce. Add the sour cream and stir until melted and smooth. Add the cream/milk and cheese. Stir until the cheese is melted. If the mixture is not thick enough, boil for another few minutes. Add the green beans.
Spoon into the casserole dish and bake 25-30 minutes or until the beans are fork tender.
Meanwhile, separate the shallot slices into rings. In a clean skillet, melt the remaining 2 tablespoons butter and cook the shallots until golden brown. Sprinkle with some salt then place on top of casserole.