Bring a medium-size pot of water to a boil.
Once the water is boiling add the cauliflower florets and cook about 12 minutes, until tender.
While the cauliflower is boiling, heat 1/3 of the butter in a small skillet over medium heat. Add garlic and sauté until fragrant, for about 2 minutes.
Strain the cauliflower and place into a blender or food processor with broth, horseradish, salt, and remaining butter. Blend until smooth.