(stolen from Alton Brown)
2 medium yellow or brown onions, thinly sliced
1/4 C flour
2 T bread crumbs
1 t Kosher salt
For the beans and sauce:
2T plus 1t Kosher salt, divided
1 lb fresh green beans, rinsed, trimmed and halved
2 T butter
12 oz mushrooms, trimmed and cut into 1/2 inch pieces
1/2 t pepper
2 cloves garlic, minced
1/4 t nutmeg
2 T flour
1 C chicken broth
1 C half and half
Preheat oven to 475 F.
Coat an aluminum baking sheet w/ cooking spray.
Place all topping ingredients into a large mixing bowl and toss to combine. Evenly spread the mixture on the cooking sheet. Bake until golden brown, approx 30 minutes, tossing 2-3 times during cooking. When they are done, remove from oven and set aside. Reduce oven to 400 degrees.
While the onions are cooking, bring a gallon of water + 2 T salt to a boil in a large pot. Blanch the beans for 5 minutes, drain, then shock them in ice water to stop the cooking. Drain and set aside.
Melt the butter over medium high heat. Add the butter, mushrooms, 1 t salt and pepper and cook, stirring occasionally, until the mushrooms start to release liquid (4-5 minutes). Add garlic and nutmeg, cook 1-2 minutes. Sprinkle flour over the mixture and stir to combine. Add chicken broth. Simmer for 1 minute. Decrease the heat to medium low and add the half and half. Cook until the mixture thickens, stirring occasionally.
Remove from heat. Stir in 1/4 of the onions and all of the green beans. Transfer to an oven safe dish. Top w/ remaining onions and cook until bubbly, approx 15 minutes.