Preheat oven to 325°F
Pat short ribs dry
Season with salt and pepper
Heat oil in a heavy pot over medium-high heat
Sear short ribs on all sides until browned
Remove short ribs from pot
Add chopped onion, carrot, and celery
Cook until softened
Add garlic and cook briefly
Stir in tomato paste
Add red wine and scrape up browned bits
Add beef broth, thyme, and bay leaves
Return short ribs to pot
Cover and transfer to oven
Braise for 2.5 to 3.5 hours until tender
Remove short ribs from pot
Strain or skim sauce if desired
Simmer sauce to thicken if needed
Serve short ribs with sauce