In a large soup pot over medium-high heat, sear and crumble beef with one tablespoon of the butter and Montreal seasoning until no longer pink. Remove meat and set aside, but do not drain fat. In same pot, add the remaining butter over medium heat and sauté onion, until tender, about 10 minutes. Add the garlic and stir. Cook for 2 minutes. Sprinkle the flour over onions and stir cooking for 3-5 minutes. Add the milk, beef stock and stir to combine. This is the soup base.
Stir in the cheese until melted and smooth. Add celery, potatoes, cooked beef and bring to a boil. Reduce heat to simmer, cover and cook until potatoes are tender, 10-12 minutes.
Serve with diced pickles sprinkled on top.
I generally purchase ground beef (80/20) fat ratio.
I make my own Montreal Seasoning which has less salt in it than store bought. Link is here.
2 large russet potatoes should make about 4 cups total.