Preheat oven to 375 degrees F.
Season the short ribs with salt and pepper. In a large Dutch oven or soup pot over medium-high heat, add the oil. Sear the ribs on all sides until well colored and slightly charred. Remove the ribs from pan to a plate and set aside.
Over medium-low heat, add the onions to the Dutch oven and cook for 1 to 2 minutes. Add the red wine and vinegar and reduce liquid by half. Stir in the tomatoes, stock and fresh herbs. Add the short ribs and cover the pot. Put in the oven and cook until meat is fork tender, about 90 minutes. Remove from oven, transfer the short ribs to a large bowl and shred the meat. Assemble the sandwiches on brioche buns with slaw. Skim the fat from the cooking liquid, strain into a serving bowl and use for dipping the sandwiches.
In a large bowl, mix together all ingredients. Allow to sit in refrigerator for 30 minutes before serving. Serve on top of sandwiches.