Heat oil in an ovenproof pan on the stove. Add onions, ginger, garlic then add dry spices and cook for 5 minutes.
Add tomatoes and chicken stock and cook for 5 minutes, then add potatoes, sautéed eggplant, raisins, chickpeas and lime leaf.
Cover with tin foil and place in the oven for 15 minutes, while this is cooking heat vegetable stock and pour over couscous. Cover with the glad wrap for 15 minutes then fluff up using a fork.
Remove tagine from oven and serve immediately with yogurt.