Begin by preheating your oven to a gentle 120°C (225°F, gas mark 1), setting the stage for a slow, tender cooking process. Remove the beef from the refrigerator to let it come up slightly to room temperature — this helps with even cooking. Meanwhile, finely pulse the onions and garlic in a food processor until they’re chopped into small, uniform pieces; this will ensure they melt smoothly into the sauce. Heat 2 tablespoons of olive oil in a large heavy casserole over medium heat. Carefully sear the beef on all sides until each surface is beautifully golden brown. This step locks in the flavors and juices. Once browned, transfer the beef to a plate and set aside. Add a small splash of olive oil to the casserole and brown the chorizo until it releases its enticing, smoky oils and becomes crisp around the edges. Remove the chorizo and set aside. Now add the chopped onions and garlic to the chorizo-infused oil; the seasoned oil will enhance their sweetness. Stir in the cumin, allspice, cloves, cinnamon stick, bay leaves, oregano, and ancho chillies, allowing the spices and herbs to toast slightly and perfume the onions. Season the mixture generously with salt and freshly ground black pepper. Pour in the balsamic vinegar to introduce a tangy depth, followed by the crushed plum tomatoes, tomato ketchup, and dark brown sugar to balance acidity and add a touch of sweetness. Stir everything together to blend the vibrant flavors. Return the beef along with its juices and the browned chorizo to the pot. Pour in 400ml of water or red wine if you want a richer taste. Bring the mixture gently up to a simmer on the stovetop. Cover the casserole and transfer it to the preheated oven. Let it cook slowly for two hours, allowing the beef to become tender and the flavors to meld beautifully. After two hours, check the meat’s tenderness and stir in the borlotti beans to the pot. Return to the oven uncovered and continue cooking for another hour to let the beans absorb the delicious sauce. Just before serving, use two forks to shred the beef gently, mixing it back into the sauce to create a luscious, hearty texture. TIP: If you prefer a thicker sauce, remove the lid for the last 30 minutes of cooking to allow excess liquid to evaporate. Serve this chilli alongside crusty bread or creamy polenta to soak up the sumptuous juices.