Heat 1 tbsp oil in a pan, and fry the prawns over medium-high heat for 2 minutes, until their moisture evaporates and they turn pink; don't cook them longer, or they'll turn rubbery.
Heat the remaining oil, and fry the onion over high heat for 8–10 minutes, until golden.
Add the tomato, ginger-garlic paste, hot paprika, turmeric, salt, cloves, cardamom, and cinnamon. Cover and simmer over medium heat until it forms a sauce, about 10–15 minutes.
Once the sauce turns reddish and the onion has softened, add the potatoes and 1 cup (250 ml) water, and simmer for 15 minutes until the potatoes are tender.
Uncovered, cook over high heat until the oil separates from the sauce. Add the ground cumin, pepper, garam masala, and nutmeg.
Add the fried prawns and a little coriander, toss together, and heat for 1 more minute over very low heat.