Make a smooth paste out of the garlic, red chillies, tomatoes and the spices.
In a pan, heat the ghee and fry the onions until golden brown.
Add in the spice paste and saute until everything is mixed well.
Add in the prawns into this mixture along with a little water and allow them to cook for 5 - 7 minutes until tender.
Add in the slit green chilies and the vinegar. Simmer for another 3 - 5 minutes and then set aside.