Marinate the mutton with 2 tbsp mustard oil, turmeric powder, ginger garlic paste, a pinch of salt and the yoghurt. Keep it in the fridge for at least 2 hours to up to overnight
Heat the remaining oil in the cooker, until it smokes, lower the flame and add the potatoes. Once they are fried and browned around the edges, remove and set them aside
Now add the whole spices in and saute´until fragrant, add the curry leaves and onions and fry until they turn light brown
Then add the marinated mutton and sear on high heat, until the meat is no longer pink
Then add the chili powder, coriander, cumin powders, tomatoes, chilis and salt. Cook this over medium high heat with 3-4 tbsp water, until the tomatoes soften
Once that happens, add the previously fried potatoes and mix well
Add enough water to just about cover the mutton and the potatoes, pressure cook over medium heat until the meat is cooked (mine took 15 minutes), then switch the flame off
Once the pressure in the cooker settles, open the lid, add the coconut milk and the coriander leaves. Let this curry simmer on medium heat for 5-7 minutes, add the garam masala and remove from flame. Check for salt and adjust if needed
Keep this covered for 10 minutes before serving. When ready, serve your delicious railway mutton curry with rice and lime wedges on the side. Enjoy!