1. Grind the garlic and the ginger to a very fine paste.
2. Cook the prawns with a little salt and a little turmeric in a sauté use until three fourths cooked. Drain and keep aside.
3. Marinate the prawns with the yoghurt , chilly powder, garam masala powder, garlic ginger paste, turmeric powder and the salt for about 2 hours.
4. Place in a greased plate
5. Liberally apply butter on the prawns.
6. Cook in a griller or a oven cum griller till the prawns turn golden brown in colour.
7. Serve garnished with the onion rings and slices of lemon.