Preheat the oven to 200°C (fan).
Chop the leek into approx. 1-inch rounds. Rinse thoroughly and drain well. Drain and rinse the chickpeas.
Toss the leek rounds with a pinch of salt and ½ tbsp oil. Place in a high-sided lasagna dish (approx. 30cm x 22cm x 5cm) and bake in the oven for 10 minutes.
While the leeks are roasting, chop the ½ head of cabbage into quarters, removing any outer leaves that are blemished. Heat 1 tbsp oil in a large, flat pan over medium-high heat. Once the pan is hot, add the cabbage quarters, cut-side down. Sprinkle with salt and leave to cook without moving for 3-4 minutes per side, turning carefully to achieve a nice char. Add 1 tbsp tamari and 4 tbsp water to the pan, allowing it to steam and deglaze, which will soften the cabbage slightly.
Remove the leeks from the oven. Add the coconut milk, chopped tomatoes, spices, and ¾ tsp salt, and mix well. Stir in the chickpeas. Nestle the cabbage pieces between the chickpeas, ensuring the sauce comes halfway up the cabbage. Return the dish to the oven for 15 minutes, or until the sauce is bubbling and the cabbage has crisped up slightly.
Serve with your favourite whole grain, such as brown rice or quinoa, and enjoy!