In a large stockpot, melt butter over medium-high heat. Add red onions and saute until transluscent. Add garlic for the last 60 seconds of cooking.
Add bacon, cauliflower, potatoes, and chicken broth to pot. Boil for about 10 minutes or until potatoes and cauliflower can be mashed with the back of a spoon.
Using an immersion blender, puree the soup until smooth.
Slowly stir in the half and half and season with salt and pepper.