Preheat oven to 350 degrees F. Cook bacon over medium heat until browned and crisped. Transfer bacon to a paper towel lined plate then discard all but 2 Tablespoons of bacon drippings. Saute onions in remaining bacon drippings until softened, about 5 minutes, stir in garlic and cook for a minute. Reduce heat to low. Boil green beans in pot for 2 minutes. Add beans to onions and garlic along with the crisped bacon.
To make sauce melt butter in a medium saucepan over medium heat. Whisk in flour, salt and pepper until well combined then whisk in chicken broth until thick and creamy, for about 3-4 minutes. Once hot and creamy stir in shredded cheese until melted. Lay one pie crust in the bottom of the pie plate before transferring beans. Pour cheese sauce over beans then transfer to a 9 inch pie plate. Put the second pie crust over the top of the beans mixture and seal with fingers like you would a pie. Cut 4-5 slits to allow for steam to escape. Bake for 35-40 minutes or until pie crust is nice and golden. Let cool for 15 minutes before serving.