Preheat your oven to 325°F (160°C). Pat the boneless short ribs completely dry with paper towels. Season generously on all sides with salt and freshly ground black pepper.

Heat the olive oil in a large Dutch oven or oven-safe pot over medium-high heat. Sear the short ribs on all sides until deeply browned, about 2-3 minutes per side. Remove the ribs from the pot and set aside.

Add the chopped onion, carrots, and celery to the same pot. Cook, stirring occasionally, until softened and lightly browned, about 5-7 minutes. Add the minced garlic and tomato paste, and cook for another minute until fragrant.

Pour in the red wine, scraping up any browned bits from the bottom of the pot. Let the wine simmer and reduce by about half, about 3-5 minutes.

Return the seared short ribs to the pot. Add the beef broth, Worcestershire sauce, rosemary sprigs, thyme sprigs, and bay leaves. The liquid should come about two-thirds of the way up the ribs; add more broth or water if needed.

Bring the liquid to a simmer on the stovetop, then cover the Dutch oven tightly with its lid. Transfer the pot to the preheated oven.

Braise for 3 to 4 hours, or until the short ribs are incredibly tender and easily shred with a fork. Check periodically and add more liquid if necessary.

Once tender, carefully remove the short ribs from the pot and set them aside. Discard the herb sprigs and bay leaves.

If you prefer a thicker sauce, you can strain the braising liquid into a saucepan. In a small bowl, whisk together the cornstarch and cold water to create a slurry. Bring the liquid in the saucepan to a simmer, then whisk in the cornstarch slurry. Cook, stirring, until the sauce has thickened. Season with additional salt and pepper to taste.

Return the short ribs to the thickened sauce to warm through, or serve them nestled in mashed potatoes or polenta with the sauce spooned generously over the top.