Lightly spray your crock pot with non-stick cooking spray and add the green beans.
Combine the soup, milk, Worcestershire sauce, garlic powder, black pepper and parmesan cheese in a bowl and whisk together. Pour over green beans and stir to combine. Cook on HIGH* for 3 hours.
After 3 hours stir the green beans and add half of the onions, stirring to combine, and cook for an additional 1 hour. Remove lid and stir. Turn off the crock pot or turn to warm until ready to serve. Just before serving stir one more time and sprinkle with the remaining onions. Enjoy!
Notes
*Updated the recipe to cook on HIGH, rather than LOW due to so many complaints about the green beans being too firm.