In a large skillet, melt butter over medium heat.

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.