Cut the onion into thin long slices.
Dry roast the coriander seeds, fennel seeds, cumin seeds, black peppercorns, red chilis, cinnamon and cashews. I normally bring a pan to medium heat, and let the spices roast until they’re fragrant, for about 5-6 mins.
Let the roasted spices cool down, and then grind them to get a spice powder.
Set the instant pot in sauté mode. Add 1.5 tbsp oil and wait for it to heat up.
When hot, add the onions and let them sauté for 10-15 minutes or so until they are golden.
Let the onions cool down. Remove from the instant pot and grind them to get an onion paste. Set aside.
Set the instant pot in sauté mode again. Add 1 tbsp oil and wait for it to heat up.
When hot, add the lamb pieces along with ginger paste, garlic paste, salt and the roasted spice powder.
At this point, if you’d like the curry to be extra spicy, add the chili powder as well.
Stir to thoroughly coat the lamb pieces and keep cooking until the pieces have browned. This will take about 5-8 mins.
Now add the fried onion paste to the instant pot.
Mix 1 tbsp flour with the yoghurt thoroughly. This will prevent the yoghurt from curdling.
Add this yoghurt-flour mixture to the instant pot.
Stir thoroughly and add 1 cup water.
Switch the instant pot to manual high pressure for 1 hour. If you aren’t using an instant pot, cook at medium-high on a stove-top for 1.5-2 hours, until the meat is tender.
After one hour, do a quick release. Your mutton curry is ready!