In a bowl, whisk 45 g greek yoghurt, 13.5 g mustard oil, the marinade spices (0.8 g ground turmeric) and a pinch of salt.
Add 800 g leg of lamb pieces and turn until coated. Cover and chill for 1 hour, or overnight.
Blend 9 g garlic, 10 g fresh ginger and a little water to a smooth paste; set aside.
Heat 40.5 g vegetable oil in a heavy pan over medium heat. Add the whole spices for the oil (0.7 g green cardamom pods, 0.4 g cloves, 1.2 g cassia bark, 3 g dried Kashmiri chillies) and let them sizzle for 1 minute.
Add 150 g onion and fry over medium heat for 10 minutes, until soft and lightly coloured.
Stir in the garlic and ginger paste and fry for 30 seconds.
Add 15.6 g tomato purée and fry for 1 minute.
Add the lamb with its marinade and cook over medium heat for 4–5 minutes, stirring, until the meat loses its raw colour.
Stir in the ground spices for the sauce (3.6 g ground coriander, 2.6 g ground cumin, 2.5 g Kashmiri chilli powder) and fry for 6–8 minutes.
Add 300 g potato chunks and salt to taste. Cover and simmer for 1 hour, until the lamb is tender and the gravy is thick; stir now and then and more often near the end so nothing catches.
Stir in 15.3 g lemon juice and more salt if needed.
Scatter over 1.5 g roughly chopped coriander leaves. Serve warm with puris.
Steep a tiny pinch (0.1 g per 2 g turmeric) in 2 tbsp warm water; use to match the rich golden hue. Contributes an aristocratic, honeyed floral flavour rather than earthy bitterness.
Use 15% to 20% of the weight (about 1 g for every 5 to 6 g fresh cloves). Whisk into sauces; gives a savoury, toasted garlic flavour without raw pungency.
Use 20% to 25% of the weight (1 g for every 4 to 5 g fresh). Stir into the gravy; adds peppery heat and warmth, though it misses the crisp, zesty kick of raw root.
Use 1 g ground for 4 g whole (or 1 small pinch per 2 to 3 whole cloves). Add with spice powders; disperses intense warmth quickly, so use with restraint.
Allspice berries
Use 100% of the weight whole in tempering. Imparts a warm, clove-like aromatic profile combined with hints of nutmeg and cinnamon.
Use about a third of the weight (0.5 g ground for a 2.5 cm piece), stirred in with the ground spices rather than fried whole, since the powder burns quickly.
Use 1 g powder for every 1.5 g whole dried chilli; whisk with a spoonful of warm water and stir into the masala to provide identical ruby colour and mild heat.
Use 80% of the weight, finely shredded and browned slowly with a pinch of asafoetida. Replicates the bulk and natural sweetness in gravies without allium.
Use 50% of the weight and stir in near the end of cooking. Adds warmth and depth since it contains ground coriander, but introduces stronger spices like clove and cinnamon.