Preheat a Dutch oven over medium to medium-high heat and add oil. Add diced bacon, stir and cook until the fat it all rendered. Use a slotted spoon to take the bacon bits out and set it aside (leave the bacon grease in the pot.)
Add diced onion, celery, and carrots to the pot and cook until softened. Make sure to stir from time to time.
Stir in minced garlic and cook for a few seconds, until fragrant.
Sprinkle flour over the vegetables and stir until veggies are evenly coated.
Slowly pour in ale, while stirring constantly, and slowly stir for a few more seconds.
Add in Worcestershire sauce, milk, broth, bay leaf, paprika, ground mustard, salt, and pepper. Stir and bring it to simmer.
Reduce the heat to medium-low and cook for about 10 minutes. Discard the bay leaf. For smooth soup: Remove the pot from the heat and puree the soup in a blender or food processor.Or you can leave it a little chucky.
Pour back into the pot if you decided to blend it and keep the heat at medium-low.
Add the cheese one handful at a time while stirring slowly and constantly (do not let it boil). Keep stirring until all cheese is melted.
Take off heat and garnish with bacon bits and croutons!