- Preheat oven to 300℉.
- In a Dutch oven heat oil over medium heat. Add short ribs in batches and brown well on all sides, about 20 minutes total. Pour off the fat.
- Transfer short ribs to a plate. Pour broth into Dutch oven and use a wooden spatula to scrape brown bits from bottom of pan. Stir in tamari, sweetener, ginger, green onions, and garlic. Return short ribs to pan. Cover and bring to a boil over high heat, then place Dutch oven in preheated oven. Cook for 2 hours.
- While short ribs cook, make the gremolata. In a small bowl stir together cilantro, garlic, and lime zest. Set aside.
- About 20 minutes before short ribs are done, make mashed cauliflower. In a large saucepan combine cauliflower, milk, garlic, and salt. Bring to a boil, then reduce heat, cover, and simmer until cauliflower is very tender, about 10 minutes. Mash or puree with a hand blender in the pan, or transfer to a food processor to puree. Stir in sour cream, butter, and pepper.
- Transfer short ribs to a serving platter. Strain the braising liquid, then remove fat from the top with a spoon or ladle or use a gravy separator.
- Serve short ribs over mashed cauliflower. Spoon over some of the braising liquid, and top with gremolata.