Preheat your oven to 350 degrees

To a pot of boiling water add 1 teaspoon of salt then add the green beans and allow them to cook for 3 minutes

After 3 minutes remove the beans from the pot then rinse them with cold water and set them aside until later.

Add two tablespoons of butter to a frying pan then saute the onions for three minutes.

Now add the mushrooms then season with one teaspoon of salt and one teaspoon of pepper and allow it to cook for an additional four minutes.

After cooking for four minutes remove it from the frying pan then set it aside until later.

Add the remaining four tablespoons of butter to the frying pan.

Mix in the flour and cook for one minute stirring frequently.

Stir in the beef broth and then the milk.

Return the onion and mushrooms then allow it to simmer for four minutes on low heat.

Add the green beans to a casserole dish then pour the gravy over the beans and mix well.

Transfer to the preheated oven and allow it to cook for 20 minutes.

After 20 minutes remove it from the oven then top it with the fried onions then return the casserole to the oven to bake for a final 5 minutes.