Step 1Heat olive oil in a large flameproof casserole dish over medium-high heat. Add chicken and cook, turning, for 3–4 minutes, or until browned; remove from pan and set aside.
Step 2Add onion, garlic, chilli flakes, anchovies (if using) and rosemary sprigs to dish; cook, stirring, for 2–3 minutes, or until onion softens. Stir in passata, bay leaves and half the balsamic vinegar with 1 1/2 cups water; bring to the boil.
Step 3Return the reserved chicken to dish; cover and simmer for 2 hours, or until chicken starts to fall off the bone and sauce thickens slightly. Stir in the olives.
Step 4Meanwhile, cook spaghetti in a large saucepan of water according to packet instructions, adding broccolini to the pasta for the last 2 minutes of cooking time. Remove broccolini and immerse in cold water; drain well. Drain the pasta.
Step 5Combine broccolini with rocket, fennel and onion in a bowl; drizzle with remaining balsamic vinegar and toss.
Step 6Divide stew, pasta and salad among 4 serving plates, garnish with parsley and serve.