Clean and devein 500 grams of prawns, leaving the tail intact. Pat them dry with a paper towel.
In a mixing bowl, combine 2 tablespoons of ginger-garlic paste, 1 teaspoon of red chili powder, 1/2 teaspoon of turmeric powder, 1 teaspoon of garam masala, 1 tablespoon of lemon juice, and salt to taste. Mix well to form a marinade.
Add the prawns to the marinade and mix well, ensuring that each prawn is coated evenly. Allow the prawns to marinate for 20-30 minutes.
In a separate bowl, mix 1/2 cup of besan (gram flour), 1/4 cup of rice flour, and a pinch of salt. Gradually add water to form a thick batter.
Heat oil in a deep frying pan over medium heat. Dip each marinated prawn into the batter, ensuring it is well coated.
Carefully place the coated prawns into the hot oil and fry them until they turn golden brown and crispy. This should take about 3-4 minutes per side.
Use a slotted spoon to remove the fried prawns from the oil and place them on a paper towel to drain any excess oil.
Serve the fried prawns hot with a side of mint chutney or ketchup.