Step 1

Combine lamb, yoghurt, garlic and ginger in a non-reactive container, season to taste with salt and a good grind of black pepper, mix well and refrigerate overnight to marinate.

Step 2

Heat oil in a large casserole or wok over medium heat. Add onion and cook, stirring occasionally, until translucent (10-15 minutes). Meanwhile, pound coriander and cumin seeds with a mortar and pestle until finely ground. Add to casserole with remaining spices, stir until fragrant (1-2 minutes), then add lamb, stirring and turning to coat (1-2 minutes). Add curry leaves, buttermilk and stock, bring to a simmer, then reduce heat to low and cook, covered for 2 hours. Add chickpeas and cook, uncovered, until softened and lamb is very tender (30-40 minutes). Transfer lamb to a bowl and strain sauce through a sieve, reserving solids.

Step 3

Return sauce to casserole, place over high heat and cook, skimming occasionally, until reduced by two-thirds (30 minutes). Add kale and coriander and return lamb and reserved solids to casserole. Serve with curry leaves, roti and cucumber-mint yoghurt.