Heat oil in a large frying pan over medium-high heat.
Add potatoes. Stir fry for about 3 minutes or until the potatoes are browned on all sides.
Add onions. Saute, stirring occasionally, for about 3-4 minutes or until the onions are browned.
Add mutton, ¾th of the spice mix, ground turmeric, and red chili powder. Stir to combine. Season with salt.
Stir fry for about 5-6 minutes.
Add remaining ginger garlic paste and tomatoes. Saute, stirring occasionally, for about 3-4 minutes or until the tomatoes are mushy.
Add mutton, tamarind paste, fried potatoes and water. Cover and cook for about 45 minutes or until mutton is tender.
Add remaining spice mix. Stir in coconut milk.
Simmer for about 3 minutes.
Garnish with coriander (cilantro) leaves.
Serve with rice or paratha.