Heat the oil and ghee in a large pot over medium heat. Cook the cumin seeds in the oil until the seeds begin to change color. Add the onion; cook and stir until translucent, about 5 minutes. Stir in the garlic and ginger; cook until the onions brown, about 5 minutes. Stir in the tomato, tomato paste, garam masala, turmeric, serrano pepper, and water; cook another 5 minutes. Lay the chicken into the sauce; mix to coat the legs. Cover; reduce heat to medium-low; cook until chicken is no longer pink near the bone, about 40 minutes. Garnish with cilantro to serve.