Wash your fresh green beans in cold water. Trim the ends off using a sharp knife. Cut them into bite-sized pieces for easy eating.
Fill a large pot with water and salt. Bring the water to a rolling boil quickly. Cook the beans for about five minutes only.
Drain the hot beans in a large colander. Place them in a bowl of ice water. This stops the cooking and keeps them green.
Melt butter in a large skillet over heat. Add the sliced mushrooms and the chopped garlic. Cook until they are soft and very brown.
Sprinkle the flour over the cooked mushroom mix. Stir it for one minute to cook flour. Slowly pour in broth and the heavy cream.
Keep stirring the sauce with your metal whisk. Let it simmer until it becomes thick and bubbly. Season it with salt and black pepper now.
Add the drained green beans into the skillet. Stir gently to coat every bean with sauce. Add half of the fried onions in too.
Pour the mixture into your greased baking dish. Spread it out so the top is flat. It is now ready for the final bake.
Place the dish in a preheated hot oven. Bake at 350 degrees for twenty minutes total. The sauce should be bubbling around the edges.
Take the dish out of the oven carefully. Sprinkle the rest of the onions on top. Bake for five more minutes until they brown.