Sear the ribs: Pat the short ribs dry with kitchen paper — this is crucial for a good crust. Heat the vegetable oil in a large, heavy-based pot or pressure cooker over a medium-high heat until it shimmers. Add the ribs in a single layer, working in batches if needed. Sear each side for 3-4 minutes until deeply browned and crusty. You'll hear a satisfying sizzle, and the meat will release a nutty, toasty aroma. Transfer the ribs to a plate.

Sweat the vegetables: Reduce the heat to medium. Add the onions, carrots, and celery to the pot. Cook for 5-7 minutes, stirring occasionally, until they soften and turn translucent. The onions should look glossy and smell sweet, not burnt. Add the garlic and cook for another minute until fragrant.

Build the base: Stir in the tomato purée and cook for 2 minutes. It will darken in colour and smell intensely rich. This step removes the raw, tinny taste of the purée and adds depth.

Deglaze and add liquid: Pour in the beef stock and balsamic vinegar, using a wooden spoon to scrape up all the browned bits stuck to the bottom of the pot. Those bits are packed with flavour. Bring the liquid to a gentle bubble — you should see small, lazy bubbles breaking the surface, not a rolling boil.

Braise the ribs: Return the seared ribs to the pot, nestling them into the liquid. Add the rosemary, thyme, and bay leaves. If using a pressure cooker, lock the lid and cook on high pressure for 45 minutes. If using a regular pot, bring to a gentle simmer, cover with a tight-fitting lid, and cook on the hob over the lowest possible heat for 1 hour 30 minutes to 1 hour 45 minutes. The liquid should barely tremble. When done, the meat will have pulled away from the bone slightly and feel tender when pierced with a fork.

Rest and finish: Turn off the heat and let the pot sit, covered, for 15 minutes. This resting time allows the fibres to relax and reabsorb juices. Remove the ribs to a warm plate and discard the herb sprigs. If you want a thicker sauce, bring the braising liquid to a boil and let it reduce by about a third, or stir in the cornflour slurry and simmer for 2 minutes until it coats the back of a spoon. The sauce should look glossy and feel velvety.