Heat oil in a pressure cooker and add the cumin seeds and the whole spices. Sizzle for a minute.
Add the onion and fry till golden brown. Add the ginger garlic paste and fry for a minute.
Add the tomato and the powders and cook till the tomato is completely mashed. Sprinkle water to avoid sticking to the bottom of the pan.
Add the washed meat and toss well to coat. Add a cup of water and season with salt. Close the lid and pressure cook for two whistles. Switch off and allow pressure to go on its own.
Meanwhile, soak the potatoes in hot water. Open the cooker, at this time the mutton would be partly cooked. Add the potatoes and the whisked yogurt. Close and cook for one whistle on medium heat. Switch off and allow the pressure to go by itself.
Notes
If you prefer a gloopier curry like seen in the pics, then cook the mutton and potatoes together. Whisk in the yogurt at the end and cook for a couple of minutes.