Set a 14-inch saute pan over medium heat. Add the ghee and toast the mustard seeds and cumin until fragrant, about 2 minutes. Add the onions, chiles, ginger and garlic and saute, stirring occasionally, until the onions are slightly caramelized, about 6 to 8 minutes. Add the tomato paste to the pan and cook for 2 minutes more. Pour the diced tomatoes into the pan and cook until reduced by about half, 3 to 4 minutes. Raise the heat to high, and add the coconut milk. Cook the coconut milk until reduced by half, about 3 minutes. Season the shrimp with 1 1/2 teaspoons of the salt. Add the shrimp to the pan, stirring often, and cook until curled and pink, about 5 minutes. Add the chopped cilantro and season with the remaining salt. Serve the shrimp over steamed basmati rice.