Use the professionally cleaned and prepared trotters and head meat described in the ingredient list. Check for visible loose bone fragments. Keep the head meat refrigerated while starting the trotters. Put the trotters in a heavy pot of about 6 litres capacity with the 2 litres water, quartered onion, broth ginger and garlic pastes, salt, cinnamon, both types of cardamom, cloves and bay leaf. The water should just cover the pieces; add a little more if needed.

Bring to a boil over medium to high heat, skimming off the foam that rises. Reduce the heat to a gentle simmer with occasional small bubbles. Cover and cook for 2 hours, checking every 45 to 60 minutes. Stir along the bottom and top up with hot water in 100 to 200 ml portions when necessary to keep the pieces submerged. Do not leave the hob unattended.

Add the refrigerated head meat, bring the liquid back to a gentle boil, then reduce the heat and cover again. Simmer for another 2 to 3 hours, checking the liquid level and tenderness. The meat should be easy to separate with a spoon, and the skin and connective tissue around the trotters should feel soft when pressed with a fork. If the head meat becomes tender first, transfer it with a slotted spoon into a covered bowl with a little hot broth while the trotters finish; return it promptly in Step 7. If the trotters remain firm, continue simmering and check every 30 minutes.

When the trotters are tender, keep the broth at a very low simmer. In a separate frying pan, heat the ghee over medium heat. Add the chopped onion and cook for about 12 to 15 minutes, stirring frequently, until evenly golden. Lower the heat if the onion starts catching.

Stir the masala ginger and garlic pastes into the onion and cook for 1 minute. Add the coriander, cumin, Kashmiri chilli powder, hot chilli powder, turmeric and black pepper. Stir over low heat for about 30 seconds, then add 2 tbsp broth from the pot to prevent scorching.

Keep the frying pan over low heat and add the whisked yoghurt a spoonful at a time, stirring after each addition. Cook for about 8 to 10 minutes, stirring frequently, until the mixture has thickened and small beads of fat appear at its edges. Add a spoonful of broth if it starts sticking. Small yoghurt flecks do not ruin the stew.

Transfer all the masala into the broth pot. Return any head meat set aside, including its juices. Stir gently and simmer uncovered for 20 to 30 minutes so the flavours combine. Add the garam masala for the final 5 minutes. If the broth is too thin, simmer a little longer; if too concentrated, add hot water in small amounts. Aim for a flowing broth with a lightly sticky feel, rather than a thick curry paste. The meat must be thoroughly cooked; a clean probe in a thick piece should read at least 75°C for 30 seconds.

Remove the cinnamon, bay leaf, cardamom pods and any visible cloves. Check for loose bone fragments and taste before adding more salt. Warm the naan if using. Divide the head meat, trotters and broth between four bowls and offer ginger, chilli, coriander and lemon separately. Explain that the trotter bones are not eaten.