To begin, brown the ground beef with the onions in a skillet until it is cooked through, about 8 minutes.
Drain off any excess grease and place the beef & onion in the slow cooker with the garlic, carrots, potatoes, beef broth, ketchup, mustard, salt, pepper, and chipotle pepper.
Stir it all together and cover. Cook on high for 4 hours or low for 8 hours.
When the soup is done, melt the butter in a small saucepan over medium heat.
Whisk in the flour and let it bubble for a minute.
Pour in the milk and whisk.
Continue to cook and stir until the sauce comes to a gentle boil and thickens.
Turn the heat all the way down to low and add in the shredded cheese. Stir until the sauce is melted.
Pour this cheese sauce into the slow cooker and stir it in.
Serve topped with extra shredded cheese, some diced pickles, crumbled bacon, or whatever you like on your burger!
Enjoy!
Notes
This soup is not spicy, but if you are concerned about heat for the very little ones, reduce the chipotle to ½ tsp.