Heat a few drizzles of olive oil In a 6 quart pot or dutch oven. Brown the ground beef with the onion and carrots until no longer pink. Add garlic cooking for 1 minute longer. Drain well.
To the pot add potatoes, broth, steak seasoning ,Worcestershire sauce and thyme. Cover and cook over medium-high for 12-15 minutes or until potatoes are fork tender.
Meanwhile, melt butter in a separate saucepan over medium heat. Add flour mixing until butter is absorbed. Add mustard, salt and pepper. Gradually whisk in milk whisking until smooth. Increase heat, stirring constantly just until milk begins to thicken, then immediately lower the heat. Allow to bubble gently for 5 minutes. Turn off heat and add cheese, mixing until melted. Keep warm.
Check potatoes for doneness. Mix in cheese sauce, dill pickles and chives. Stir until fully combined Cook uncovered over medium for 5 minutes to allow the soup to reduce and flavors combine.
Serve topped with additional cheese, chives and croutons, if desired.