In a large pot heat oil until hot. Now add the beef stew meat and season with salt and pepper. Sear on all sides until beef is browned.
Add the thyme, garlic and tomato paste. Cook the tomato paste for about 1 minute until it starts to caramelize and the raw flavour is removed. Now deglaze with red wine vinegar. Once the vinegar is almost gone, add the cabernet and reduce the wine by half.
Transfer the stew mixture to an Instant Pot or pressure cooker, add the beef broth, and cook on high pressure for 35 minutes. Slowly release the steam from pot. Add pearl onions and sweet potatoes. Place on sauté mode (or medium heat) and cook for about 7-8 minutes until potatoes are soft.
** If you don’t have a pressure cooker, place beef mixture and beef broth in an oven proof pot with lid (such as a Le Cruset pot). Place covered pot in a 350F pre-heated oven for about 1.5 hours. When beef is nice and tender, add the pearl onions, sweet potatoes and cook for 7-8 minutes until the potatoes are tender. **
Mix cornstarch and water together in a small bowl. Add cornstarch slurry to stew, cook until thickens, season with salt and pepper. Serve with Mini French Bread.