1.In a large saucepan over medium heat, melt the butter. Add the onion, carrot, celery, and garlic and saute in butter until the vegetables begin to soften, about 4 minutes. Sprinkle the flour into the pan and continue to stir for 2 minutes to toast the flour. Add salt and pepper, to taste. Gradually whisk in the stock, then the milk and the beer. Stir in the potatoes and bring the soup to a boil. Reduce the heat and simmer the soup until the potato is tender, about 20 to 30 minutes.   2.Remove the pan from the heat and using an immersion blender, puree the soup until smooth. Return the soup to low heat. Add the cheese a handful at a time, stirring until melted and smooth after each addition. Season the soup, to taste, with hot sauce, Worcestershire, and salt and pepper.   3.Divide the soup among bowls and top with sour cream, crisp bacon and chopped chives.