Preheat your slow cooker to low or preheat the oven to 150C, fan-forced. Quarter the leek lengthwise, then thickly slice (see Cooking tip). Crush or finely chop the garlic. Put the lamb in a bowl. Scatter with 1 tbs plain flour, season with pepper and toss to coat.
Step 2 — Brown lamb
Heat 2 tsp olive oil in a medium frypan (if using a slow cooker) or a medium flameproof casserole dish over high heat. Shake the excess flour from the lamb, reserving the flour. Cook the lamb, turning regularly, for 3-4 mins until browned. Remove the pan or dish from the heat.
Step 3 — Slow cooker method
If using the slow cooker, combine the lamb, leek, garlic, Tuscan seasoning, red pesto, tomato paste, reserved flour and 300ml boiling water in the slow cooker bowl. Cover and cook on low for 8 hours.
Step 4 — Casserole method
If using the casserole dish, add the leek, garlic, Tuscan seasoning, red pesto, tomato paste, reserved flour and 430ml (1¾ cups) boiling water to the lamb in the dish and stir to combine. Bake, covered, for 2½ hours or until the lamb is tender.
Step 5 — Cook pasta
About 20 mins before serving, bring a medium saucepan of salted water to the boil. Cook the pasta in the pan of boiling water for 11 mins or until al dente. Drain.
Step 6 — Serve up
Combine 2 tsp olive oil and 1 tsp red wine vinegar in a large bowl and season with salt and pepper. Add the rocket and toss to coat. Finely grate the parmesan. Taste the ragu and season with salt and pepper. Divide the pasta and ragu among bowls, scatter over the parmesan and serve with the salad. Enjoy!