Peel and finely chop the onion.
Peel and crush or finely grate the garlic and ginger, keeping these together.
Deseed and finely chop one green chilli.
Put a medium, wide and heavy-based pan on a medium-high heat and toast half a teaspoon each of the coriander and cumin seeds, until fragrant.
Tip into a mortar or spice grinder and grind to a powder.
Pour the oil into the empty pan and stir-fry the remaining whole spices until aromatic.
Turn down the heat to medium-low, then add the onion and a pinch of salt, and cook until soft and just starting to turn brown.
Stir in the garlic, ginger and chopped chilli, and fry for another couple of minutes.
Add the ground spices and fry for another minute.
Turn the heat back up to medium-high, then stir in the yoghurt and cook for a couple of minutes.
Split open the remaining finger chilli lengthways, then add it to the pot with the lamb and a teaspoon of salt.
Turn down the heat and cook until the mince begins to release its juices.
Sprinkle over the flour, stir to incorporate, then turn the heat right down and leave to cook for 20 minutes.
Towards the end of the cooking time, strip the mint leaves from their stems and finely chop the leaves.
Stir into the pan along with the peas and fry gently for about another 15 minutes.
Taste and adjust the seasoning, if necessary.
