How to Make It
Sprinkle ribs with salt and pepper. Heat 1 tablespoon oil in a large skillet over medium-high. Add half of the ribs to skillet; cook, turning occasionally, until browned on all sides, about 8 minutes. Transfer ribs to a 6-quart slow cooker; discard drippings in skillet. (Don’t wipe skillet clean.) Repeat procedure with remaining ribs. Add remaining 1 1/2 teaspoons oil to skillet; stir in mushrooms, garlic, and ginger. Cook, stirring often, until mushrooms soften slightly, about 4 minutes; transfer mushroom mixture to slow cooker. Add beef stock, brown sugar, vinegar, soy sauce, and red pepper to slow cooker. Cover and cook on low until ribs are tender, about 8 hours.
Transfer ribs to a serving platter; reserve cooking liquid in the slow cooker. Skim fat from surface of cooking liquid. Drizzle ribs with reserved cooking liquid.