Melt the butter in a large stock pot or Dutch oven over medium heat. Add the onion, carrots and garlic and add 1 teaspoon kosher salt and 1/2 teaspoon black pepper. Cook until tender, about 10 minutes. Sprinkle the flour over the onions and carrots and cook, stirring constantly, about 1 minute. Pour in the stock, dijon mustard and Worcestershire sauce and simmer until the vegetables are very soft, about another 10 minutes. Add the beer and simmer 5 minutes. Puree with an immersion blender until smooth. (If you do not have an immersion blender, puree in a regular blender until smooth, then return pureed soup to stock pot.) Add the cheeses and half and half, and stir until completely melted and smooth.