Follow these steps in one large soup pot:

1. Brown the beef
   • Over medium​‑high heat, add 1 tbsp butter to the pot.
   • Add ground beef and sprinkle with Montreal seasoning.
   • Crumble and cook until no longer pink.
   • Remove the cooked beef from the pot and set aside, leaving the fat behind (do not drain).
2. Sauté onion & garlic
   • In the same pot, add the remaining 3 tbsp butter over medium heat.
   • Add the chopped onion and sauté until tender and translucent, about 8–10 minutes.
   • Stir in the garlic and cook 1–2 more minutes until fragrant.
3. Make the roux / base
   • Sprinkle the flour over the onions and garlic. Stir well so the flour coats the vegetables.
   • Cook and stir for 3–5 minutes, allowing the flour to cook slightly (this helps avoid a raw flour taste).
4. Add liquids & combine
   • Slowly pour in the milk while whisking or stirring continuously to prevent lumps.
   • Add the beef stock and stir to combine thoroughly. This creates your soup base.
5. Incorporate cheese & vegetables
   • Add the shredded cheddar cheese, stirring until melted and smooth.
   • Then fold in the diced celery, cubed potatoes, and the reserved cooked beef.
6. Simmer
   • Bring the soup to a gentle boil, then reduce heat to a simmer.
   • Cover and cook until the potatoes are tender—10–12 minutes.
   • Check and stir occasionally to prevent sticking.
7. Serve & garnish
   • Ladle into bowls and sprinkle the ½ cup diced dill pickles on top for a refreshing tang.