Trim the desired amount of fat off the lamb (I leave some for richness and flavour) and then cut into big chunks. Do not throw away the bones.
Season the lamb with 1 tsp of salt and freshly cracked pepper.
In a non-stick pan on high or in you pressure cooker on saute, add 2 tbsp of oil and sear the lamb chunks including the bones in batches (Note 2). Set the cooked lamb aside.
Turn the heat down to medium (ignore if using a pressure cooker) and add the onion. Saute for a minute.
Add the celery and cook for roughly 3 minutes.
Take the pan off the heat / turn off your pressure cooker and let it cool down for a few minutes.
Add some of the Passata (1/2 cup or so) to deglaze the pan. (Be careful of the steam or splash back generated if the pan or pressure cooker is still too hot!)
Add the lamb, bones, onions, garlic, celery, rosemary, bay leaf, sugar and the remaining Passata into the pressure cooker.
Turn on the pressure cooker and cook for 30 mins on high / stew setting.
Start cooking enough jasmine rice for everyone. (Note 3)
After 30 mins, carefully depressurise the pressure cooker according to your user manual and remove the lid.
Remove the bones, bay leaves and any unwanted fat.
Add the carrots and potatoes to the pressure cooker. Put the lid back on and cook for another 10 minutes on high pressure / stew setting.
After 10 mins carefully depressurise the pressure cooker according to your user manual and remove the lid.
Check the sauce for seasoning and adjust accordingly.
Serve with rice and garnish with parsley.