Clean the shrimps by removing the shells but leave the tails intact. Instead of pressing them, make 2-3 small diagonal cuts across the belly (underside) of each shrimp. This helps prevent the shrimps from curling when frying, keeping them straight. Pat them dry and set aside.
In a bowl, mix the flour, cornstarch, and baking powder. In a separate small bowl, lightly beat the cold egg, then add the ice-cold water. Gradually pour this into the flour mixture, stirring gently to combine. The batter should remain slightly lumpy—avoid overmixing to maintain a light texture.
In a deep frying pan, heat oil over medium-high heat to around 170°C (340°F) to 180°C (350°F). To test if it’s ready, drop a bit of batter into the oil—if it floats and bubbles immediately, the oil is good to go.
Lightly dust the shrimps with extra flour, then dip each shrimp into the batter, ensuring they are fully coated. Carefully place the shrimps into the hot oil, frying in small batches to avoid overcrowding.
Fry the shrimps for 2-3 minutes or until they turn golden and crispy. Turn them occasionally to cook evenly. Once fried, remove them from the oil and drain them on paper towels.
Serve your shrimp tempura hot with tempura dipping sauce or soy sauce with a splash of lemon juice.