Set up your frying station with a deep-fry thermometer, a large pan filled with about 5 cm of oil, and a wire rack lined with paper towels. This setup helps keep the tempura crispy and prevents overcrowding.
Prepare the batter by whisking together the tempura flour, rice flour (if using), and a pinch of salt in a bowl. Add the ice-cold water and gently mix just until combined—lumps are okay. The batter should be cold and slightly lumpy to maximize puffiness during frying.
Peel and devein the prawns, leaving the tails on for easy handling. Pat them dry thoroughly with paper towels to remove excess moisture, which can cause sogginess.
Heat the oil over medium-high heat until the thermometer reads 170°C (340°F). Test the temperature by dropping a small spoonful of batter into the oil; it should sizzle immediately and rise within 2-3 seconds, forming bubbles around it.
Dip each prawn into the batter, allowing excess to drip off gently. Carefully lower the battered prawns into the hot oil, placing them apart to avoid sticking. Fry in batches for 2–3 minutes, turning occasionally, until the shells are golden and puffed, and the prawns are opaque and firm.
Monitor the oil temperature during frying, adjusting the heat as needed to keep it steady at around 170°C. If the batter browns too quickly, lower the heat slightly; if it remains pale, increase it.
Once cooked, use tongs to transfer the prawns onto the wire rack to drain excess oil and rest for about 1 minute. This helps maintain crispness and prevents sogginess.
Serve the hot tempura immediately, garnished with lemon or lime wedges for a bright, fresh contrast. Enjoy the airy crunch with the tender, juicy prawns inside.
