Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking dish.

Cook half a pound of bacon in a skillet over medium-low heat until crispy, about 8 to 10 minutes. Remove bacon and drain on paper towels.

Sauté a finely chopped yellow onion in the reserved bacon fat over medium heat for 5 to 7 minutes, until translucent.

Add 8 ounces of sliced button mushrooms and cook for another 5 minutes, then stir in 2 minced garlic cloves.

In a mixing bowl, combine sautéed onions, mushrooms, garlic, one can of cream of mushroom soup, crumbled bacon, and 0.5 cups of milk. Stir in 1 cup of grated Monterey Jack cheese, adding salt and pepper to taste.

Gently fold in 2 cans of drained cut green beans without crushing them.

Pour the mixture into the greased baking dish and spread it out evenly.

Sprinkle 1.5 cups of French fried onions over the top of the casserole.

Bake in the preheated oven uncovered for 30 minutes, until bubbly and golden brown.

Let sit for a few minutes before serving.