Add onion, and cook until soft, about 3-5 minutes.
Add garlic, and cook, stirring frequently, for about 30 seconds.
Pour in chicken broth.
Add cauliflower, and cover skillet (I just use a piece of foil).
Let the cauliflower steam until fork-tender, about 10 minutes.
Carefully add cauliflower and broth mixture to a blender.
Add in fat-free half-and-half and dry mustard.
Blend until smooth.
Season with salt and pepper to taste.
Stir in shredded cheese, and let melt.
Garnish with a pinch of shredded cheddar or Parmesan cheese, if desired.
You can use an equal amount of steamed frozen cauliflower florets. Simply cook the florets in their bag according to the package instructions and then stir the steamed florets into the broth. Skip covering and steaming the florets in the pan (steps 5 and 6) and then proceed with the recipe as written.