Preheat the oven to 350 degrees F.

Fry the bacon in a large skillet over medium-high heat until crispy. Add the onions and cook until soft and translucent, about 4-5 minutes. Add the mushrooms and garlic and cook for another 4-5 minutes until the mushrooms are soft. Transfer the mixture to a bowl.

Melt the butter in the same skillet and whisk in the flour. Once combined, continue whisking for another 2 minutes until the mixture has slightly deepened in color. Add the half-and-half and chicken broth while constantly whisking to prevent lumps. Once slightly thickened, add the cheese and whisk until melted and combined.

Next add the mushroom/bacon mixture along with the salt and pepper. Let the sauce simmer for a couple of minutes, then add the green beans. Stir to combine.