In a large pot heat oil until hot. Sear beef on all sides until browned. Remove beef and add onions and thyme to pot. Cook onions on low until caramelized.
Add the garlic and cook about 1 minute. Deglaze with red wine and reduce by half.
Transfer the beef and onion mixture to an Instant Pot or Pressure Cooker, add the beef broth, and cook on high pressure for 50 minutes. Slowly release the steam from pot.**
While beef is cooking, place potatoes in a medium pot and cover with cold water. Put on medium high heat and cook until potatoes start to fall apart. Strain, add warmed milk, butter and mash until smooth consistency. Season with salt and pepper.
Once beef is tender, add carrots to the beef pot and cook until they are tender.
Mix cornstarch and water together in a small bowl. Add cornstarch slurry to beef pot, cook until thickens, and season with salt and pepper.
Slice beef and serve with glazed carrots, mashed potatoes, and braising sauce.
**If you don’t have a pressure cooker, place beef, onion mixture and beef broth in an oven proof pot with lid (such as a Le Cruset pot). Place covered pot in a 350°F pre-heated oven for about 2.5 hours.
When beef is tender, remove and follow the remaining instructions.