Heat the oil in the pressure cooker and add the pureed onions. Fry the onions until quite dark, you will need to keep stirring to ensure the puree doesn't burn as this will ruin the taste of the curry by adding bitterness. Then add the garlic and ginger and stir through.
Next you need to add the pureed tomatoes, green chillies, salt, red chilli powder and turmeric. Turn the heat to low and cook for 6-7 minutes. Keep stirring the tomato masala , if it starts to dry out, add small splashes of water. After the 6-7 minutes, you should see the oil start to separate from the masala.
Turn the heat to medium and now add the lamb to the masala and stir through. Make sure the lamb properly coats in the masala and that the lamb browns.
Then add the ground coriander, cumin, bay leaf, black peppercorns, black cardamom . Stir through and sauté the lamb for 5 minutes on low heat. Again, add splashes of water if the lamb starts to stick to the pan.
Next add the 800ml of water, bring to boil and cover the pressure cooker with the lid. Then turn the heat to medium and once you hear the whistling of the steam in the pressure cooker, time the pressure cooking for 12 minutes. The lamb should be soft after this time.
After 12 minutes, remove the pressure cooker lid, check the lamb is soft (if not let it simmer for a further few minutes on the hob) and then add the garam masala and stir through.
Add the freshly chopped coriander and serve!