For the Short Ribs, heat oil in Dutch oven or large deep skillet on medium-high heat. Add 1/2 of the short ribs; cook 5 to 10 minutes or until browned on all sides. Place in slow cooker. Repeat with remaining short ribs.
Mix remaining short rib ingredients, except water and cornstarch, in medium bowl. Add to slow cooker. Cover.
Cook 8 hours on LOW or 4 hours on HIGH or until short ribs are tender.
Mix water and cornstarch in small bowl with wire whisk. Stir into slow cooker. Cover. Cook 15 to 30 minutes on HIGH, or until sauce is thickened.
Meanwhile, for the Polenta, bring stock, milk and salt to boil in large saucepan. Whisking constantly, add polenta in thin stream. Reduce heat to low; stirring constantly, simmer 3 to 4 minutes or until thickened. Remove from heat. Stir in cheese, butter and chives. Serve short ribs over polenta.