Preheat oven to 350 degrees. Lightly grease a casserole dish with olive oil spray.

Fill a large pot with 1 - 2" of water, and bring to a boil. Cut cauliflower into bite-sized pieces and add to boiling water, cover, and reduce heat to low. Allow to simmer/steam for 8 - 10 minutes, or until fork tender. Strain the cauliflower well.

Meanwhile, cook bacon until crisp. Remove bacon and crumble, reserving the bacon grease.

Pour cauliflower into casserole dish, and pour bacon grease on top. Add in sour cream, half of the shredded cheese, and half the crumbled bacon and stir until well coated. Top with remaining cheese and bacon, and bake in preheated oven for 15 - 20 minutes, or until cheese is melted.