Divide the chicken broth into two parts. Dissolve the wheat flour in one of the broth halves. Stir with a hand mixer and make sure the mixture is lump-free. Reserve this portion. Note: the wheat flour should not be dissolved directly in the soup because lumps may form.
Turn the stove on to medium-high heat, set a large pot, and pour the butter into the pot. When the butter is melted, add the finely chopped onions. Cook for a few minutes until the onions turn transparent.
Add the diced carrot and sauté for a few minutes.
Pour half of the broth that does not contain wheat flour into the pot. Cook for ten minutes or until carrots is tender. Add the cream, mustard, Worcestershire sauce, salt, and pepper. Stir well.
When the cream has melted, add the beer.
Lastly, add the broth with wheat flour to the pot. From this point on, you cannot stop beating to prevent lumps from forming. Cook for a few minutes until the soup is thick and ready.
To serve, slice the top of a round loaf like a lid. And with a fork scrape the inside of the bread being careful not to break its walls. Remove all the bread crumbs (you can use them for dipping in soup). Pour the soup into the cavity of the bread, top with a little extra cheese of your choice, and if desired, gratin it for a few minutes in the oven.