Place the star anise, cloves and thyme in one layer of cheesecloth. Tie in a bundle. Set aside.
In a saucepan, soften the onion and garlic in the butter. Add the curry powder, ginger and meat. Coat with the spices. Season with salt and pepper.
Add the broth, carrots, turnip, tomato and spice bundle. Bring to a boil and simmer over medium heat for 30 minutes. Remove the spice bundle. Adjust the seasoning. Set 60 ml (1/4 cup) of sauce aside. Transfer the curry in a 33 x 23-cm (13 x 9-inch) baking dish.
With the rack in the middle position, preheat the oven to 170 °C (325 °F).
With a mandolin, thinly slice the potatoes and arrange in a rosette on the lamb. Drizzle with reserved pan juices. Season with salt and pepper. Bake for about 2 hours.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.