pounds bone-in beef short ribs, cut crosswise into 2-inch pieces
Kosher salt and freshly ground black pepper
3tablespoons vegetable oil
3medium onions, chopped
3medium carrots, peeled, chopped
2celery stalks, chopped
3tablespoons all-purpose flour
1tablespoon tomato paste
1750 ml bottle dry red wine (preferably Cabernet Sauvignon)
10sprigs flat-leaf parsley
2fresh or dried bay leaves
1head of garlic, halved crosswise
4cups low-salt beef stock
Preheat oven to 350°. Season short ribs with salt and pepper. Heat oil in a large Dutch oven over medium-high. Working in 2 batches, brown short ribs on all sides, about 8 minutes per batch. Transfer short ribs to a plate. Pour off all but 3 Tbsp. drippings from pot.
Add onions, carrots, and celery to pot and cook over medium-high heat, stirring often, until onions are browned, about 5 minutes. Add flour and tomato paste; cook, stirring constantly, until well combined and deep red, 2-3 minutes. Stir in wine, then add short ribs with any accumulated juices. Bring to a boil; lower heat to medium and simmer until wine is reduced by half, about 25 minutes. Add all herbs to pot along with garlic. Stir in stock. Bring to a boil, cover, and transfer to oven.
Cook until short ribs are tender, 2–2½ hours. Transfer short ribs to a platter. Strain sauce from pot into a measuring cup. Spoon fat from surface of sauce and discard; season sauce to taste with salt and pepper. Serve in shallow bowls over mashed potatoes with sauce spooned over.