Instructions

1. Bring a pot of water to boil and add in green beans. Cook until tender and remove from heat.
2. Meanwhile, in a skillet, melt 4 tablespoons of butter over medium heat. Whisk in the flour and cook, whisking constantly for about 2 minutes until the mixture is smooth and has darkened.
3. Slowly drizzle in milk, whisking constantly. Bring to a simmer and cook, stirring, until the sauce thickens slightly.
4. Remove skillet from heat and sprinkle in the gruyere and parmesan cheeses. Season to taste with salt and pepper. Stir in green beans then transfer to a serving dish.
5. In a skillet melt the remaining 2 tbsp butter on medium heat. Sprinkle in bread crumbs and cook, stirring often, for 3 minutes until golden brown. Sprinkle crumbs over green beans and serve.