Boil the potatoes and carrots until soft, drain and keep aside.
Heat the oil in a kadai (wide and deep saute pan), add the mustard seeds and let them splutter. Add curry leaves and give it a quick stir. Add the onions and ginger garlic paste.
Saute till the onions are cooked and light brown. Add the crushed spice mix, turmeric powder and cayenne.Saute till the raw smell of the spices go away.
Add the tomatoes and saute till they are soft.
Now add the salt and black pepper and mix well.
Add the cooked potatoes and carrots along with coconut milk, mix well and let it start to steam. Dont let it come to a boil, as the coconut milk might separate. Remove from heat and garnish with cilantro.
Serve hot with rotis, naans or rice.