In the Le Creuset Clover Cocotte, or another Dutch oven that is at least 2 1/2 quarts, heat olive oil. Once hot, add onion and cook until softened and brown, approximately 15 to 20 minutes, stirring constantly. Add garlic and cook for 1 minute.
Add flour and cook for approximately 3 to 4 minutes. Add Guinness, stirring constantly, and cook until thick and sticky, approximately 5 minutes. Add beef broth, milk, Worcestershire, and chili powder. Bring to a simmer over medium-low heat until thickened slightly, approximately 15 minutes.
Add cheese to the soup, stirring constantly until the cheese is melted and soup is smooth. Taste and season with salt and pepper as desired.
Stir in Guinness Braised Short Ribs and cook until heated through.
Keep warm until ready to serve (you can do this over the stove or in the oven in the Le Creuset Clover Cocotte!). Serve with a hearty grain bread.