Preheat oven to 350°F (180°C).
Season ribs with 1 tsp (5 mL) salt and pepper. In large oven-safe saucepan, heat oil over medium-high heat. Brown ribs in batches, 1 to 2 min. per side, transferring to plate. Place browned ribs back into saucepan, along with juices. Pour in beef broth; bring just to a boil over high heat. Turn off heat, cover with lid and bake in oven 2 hr., or until meat is tender and falling off the bone.
Transfer ribs to bowl; cool slightly. Skim and discard fat from juices in saucepan; bring to a simmer over medium heat 10 to 15 min., until it is a slightly thickened sauce. Meanwhile, shred beef with two forks; discarding bones. Remove sauce from heat; mix in shredded meat. (Note: beef mixture can be made ahead, cooled and stored in a sealed container in fridge up to 2 days. Reheat on stove or in microwave to proceed with recipe.)
In small bowl combine yogourt, horseradish, 1/2 cup (125 mL) green onions and remaining 1/4 tsp (1 mL) salt. Top each toasted baguette slice with 1 tbsp (15 mL) warm shredded beef mixture and 1 tsp (5 mL) yogourt mixture. Sprinkle with additional green onions to serve.
To make an extra spicy yogourt sauce, use equal amount of grated fresh horseradish for creamed horseradish.