Heat oil in a pan or a pot.
Add in the bay leaf, whole spices and curry leaves. Saute for few seconds.
Add in the pureed onion and ginger garlic paste and saute for about one minute.
Add in the pureed tomato, salt as per taste and saute for for 2 minutes.
Add in the spice masala powder - turmeric, red chilli, coriander, cumin, black pepper, meat masala and half of garam masala powder(half of garam masala reserve for later). Mix well and saute fora minute.
Add in the meat. Mix to combine the meat and masala well. Put on the lid and cook over low-medium heat for 5-10 minutes.
The mutton will strat releasing water and cook on its own juice. Keep stirring the dish in regular intervals so that it doesn't stick to the bottom of the pan and also cooks evenly.
Add in the potatoes. I recommend to cut them into big chunks or pieces. Mix well. Put on the lid and cook on low-medium for about 2 minutes.
Add in water as required. Mix well. Cover it and cook until the meat is tender and is cooked through, stirring them occasionally in between the cooking. Add in water if required.
It took approximately 40 minutes in total. Cooking time defer according to the tenderness of the meat.
Adjust the consistency as per your requirement. If you want more gravy add more water.
Lastly add in the slit green chillies, chopped coriander leaves and the reserved garam masala powder. Mix well for a minutes and take off the heat.