Once cauliflower is boiling, cook 10-12 minutes, or until cauliflower is fork tender. Strain cauliflower, return to pot over medium heat, and cook 1 minute to evaporate excess moisture. Add sour cream and mash with a potato masher or fork. Don't worry if cauliflower doesn't become perfectly smooth. Stir in red pepper flakes (start with half the packet, taste, and then add more, if desired) and ¼ tsp. salt. Set aside.