Wash the green beans and mushrooms. Cut the ends off the green beans and chop them down the middle. Slice the mushrooms by cutting them down the middle, laying them flat, and slicing.

Boil the green beans for 4 minutes, then drain and run them under cold water.

In the same pan, add 3 tablespoons of butter and 1 chopped onion. Set the stove to medium low and cook for about 5 minutes.

Add 2 cloves of minced garlic, the sliced mushrooms, and a big pinch of salt. Optionally, add pepper for spice. Cook for another 5 minutes until the mushrooms are cooked through.

Stir in 3 tablespoons of flour and cook for 2 to 3 minutes to incorporate the flour.

Slowly add 1 cup of chicken broth and let it simmer for a couple of minutes until it thickens.

Add 1 cup of heavy cream and grate in about 1/2 cup of Parmesan cheese.

Add the green beans to the mixture and transfer it to a greased baking dish, spreading it out evenly.

Sprinkle crispy fried onions on top and bake at 375°F for about 15 minutes.