1Blend all spices, salt, tomato paste, ginger, & garlic listed with yogurt until smooth in mixie, blender, or food processor.
2Pour mixture over mutton pieces & allow to marinate for at least 2 hours or up to overnight in the refrigerator in an airtight container.
3When ready to cook, heat mustard oil and/or ghee in pressure cooker about 5 to 7 minutes until fragrant. Fry onions for around 8-10 minutes until medium brown.
4Add cassia leaves, mutton, & marinade to fried onions in pressure cooker. Stir well. Allow to simmer over medium heat for 10 minutes.
5Add 1 cup water or stock/shorba and stir. Secure lid on pressure cooker & cook for 5-6 steams or until mutton is to desired tenderness & oil separates from sauce. Salt to taste and serve.
Don't have a pressure cooker? Then follow the above steps using a deep, heavy bottomed skillet or kadhai & simply simmer at the end until mutton is to desired tenderness & oil separates from sauce. Is mixture dries out or begins to scorch before meat is to desired tenderness just keep adding 1/2 cup water or stock as needed to prevent burning.
In Kashmir mustard oil and/or ghee are typically used in Rogan Josh along with the fatty cuts of mutton/goat, if you don't like the pungent flavor of mustard oil or don't wish to use ghee just use sunflower or canola oil.
This recipe works well using lamb or beef stew meat also.
If you live in western countries I would choose the full fat 'Greek style' yogurt to cook this with as it is the most like the yogurt/curd that is used in Kashmir.