In a bowl, marinate the chicken with yogurt, garam masala, black pepper powder, salt and lemon juice; set aside for 30 minutes.
Cashew nut paste:
Soak the cashew nuts for 15 minutes in warm water; drain and grind smooth.
In a large saucepan; heat mustard oil and add then add cardamom, cloves and cinnamon; sauté for a minute.
Now add the chopped onions, green chillies and ginger; sauté for 6-8 minutes or until the onions begin to colour.
Add the marinated chicken (saving any remaining marinade for later), sear the chicken over high heat for a couple of minutes and then reduce the heat. Add cumin powder, kasoori methi powder, cardamom powder, black pepper powder and salt; stir well and then add the remaining marinade (if any) and the cashew nut paste. Add 200 ml of water, increase the heat and bring to a boil then reduce the heat, cover and leave to simmer for 20 minutes or until the chicken is done.
Check seasoning, stir well.
Serve garnished with seared padron peppers, chilli threadsor pink peppercorns.