Step 1

Heat the oil in a large skillet over medium-high heat. Add the kielbasa and cook until browned and crisp, 1 to 2 minutes. Transfer to a paper towel-lined plate and set aside.

Step 2

Melt the butter in a large Dutch oven over medium-low heat. Add the carrots, celery, onion, garlic, mustard powder and cayenne. Cook the vegetables until tender and translucent, about 15 minutes.

Step 3

Meanwhile, prepare the bread bowls. Using a sharp knife, slice the top off of each boule to use as a topper. Hollow out the middle with a fork or your fingers, leaving a thick bread shell. Save the removed bread for another use.

Step 4

Sprinkle the flour over the vegetables and cook, stirring constantly, about 1 minute. Add the Dijon mustard and Worcestershire. Pour in the stock and beer and simmer until the alcohol cooks out, about 5 minutes.

Step 5

Puree the soup with an immersion blender until smooth. Add the Cheddar and Gruyere and stir until the cheese is melted. Season with salt and pepper. Ladle into the bread bowls and serve immediately, topped with the kielbasa croutons and chives. Use the bread toppers for dipping, if desired.