Heat a pressure cooker, add mutton, one teaspoon garlic, turmeric powder, cardamoms, cinnamon and four cups of water. Mix and add salt. Mix well, cover and cook under pressure for four to five whistles or till mutton is three-fourth done.
Open the lid when the pressure has reduced completely and strain the mutton. Discard the cinnamon and cardamoms and reserve the cooking liquor.
Heat coconut oil in a non-stick pan, add mustard seeds and let them splutter.
Add green chillies, curry leaves, remaining garlic and ginger and sauté till fragrant.
Add onions, mix and sauté till the onions turn golden.
Add mutton pieces and mix well. Add crushed peppercorns and salt and mix again.
Add four teaspoons of cooking liquor and mix well. Cook for three to four minutes.
Transfer into a serving bowl, garnish with coriander leaves and serve hot.