Clean and devein 250 grams of prawns, leaving the tails intact. Pat them dry with a paper towel and set aside.
In a mixing bowl, add 150 grams of gram flour (besan), 1/2 teaspoon of red chili powder, 1/2 teaspoon of turmeric powder, 1/2 teaspoon of garam masala, 1/2 teaspoon of ajwain (carom seeds), a pinch of asafoetida (hing), salt to taste, and 1 tablespoon of finely chopped coriander leaves. Mix well.
Gradually add water to the dry mixture and whisk until you get a thick, smooth batter. The consistency should be such that it coats the prawns well.
Heat oil in a deep frying pan or kadai over medium heat. To check if the oil is hot enough, drop a small amount of batter into the oil. If it sizzles and rises to the surface, the oil is ready for frying.
Dip each prawn into the batter, ensuring it is well coated, and carefully slide it into the hot oil. Fry the prawns in batches, making sure not to overcrowd the pan.
Fry the prawn pakoras for 3-4 minutes on each side or until they turn golden brown and crispy. Use a slotted spoon to remove the pakoras from the oil and place them on a paper towel to drain excess oil.
Serve the prawn pakoras hot with mint chutney or ketchup.