Combine pork, yogurt, onion, ginger, garlic and garam masala. Marinate for 20 minutes or overnight in the refrigerator. Heat ghee, add chopped onion and stir until onion turns golden brown. Add marinated pork and cook over high
heat for 5 minutes, stirring, occasionally. Add turmeric, Maggi fish sauce, water and bring to boil. Reduce heat; simmer covered for 30 minutes until meat is tender. Add a slurry of corn flour and extra water. Simmer for 5
minutes. Garnish and serve with coriander and sour cream.