Preheat oven to 325. Spray and 8 x 8 pan with cooking spray. Set aside.
Cut the cauliflower into florettes and add them to a microwave safe bowl. Add 2 tablespoons of water and cover with cling film. Microwave for 5-8 minutes, depending on your microwave, until completely cooked and tender. Drain the excess water and let sit uncovered for a minute or two.
(Alternately, steam your cauliflower the conventional way. You may need to squeeze a little water out of the cauliflower after cooking.)
Mash the cauliflower using a potato masher until coarse. Add half of the cheddar cheese and mix by hand. Season with salt and pepper.
3. Top the loaded cauliflower with the remaining cheese, remaining chives and bacon. Bake until hot and bubbly.