Instructions

1. Preheat oven to 350 degrees. Heat a large pot of water until boiling, then submerge green beans completely. Cook until bright green, about 5 minutes, then transfer immediately into an ice bath to stop the cooking. Drain green beans and set aside until needed.

2. In a large, heavy-bottomed pot, heat 1 tablespoon of butter until melted then add onion. Saute until just opaque then add garlic and continue sauteing until fragrant. Add sliced mushrooms to pan and cook until soft; add remaining tablespoons of butter and melt, then add flour to the pot and mix. Cook until flour no longer tastes raw, then remove from heat and add milk to the pan. Return to medium heat and whisk to combine, then whisk in dijon mustard. Allow sauce to thicken, then season liberally with salt and pepper. Add green beans to sauce and stir to combine before transferring to a baking dish.

3. Bake until bubbling, about 30 minutes. Top with French fried onions before serving.