To make dipping sauce, combine lemon rind and juice in a small bowl with ½ teaspoon sea salt and 2 teaspoons white pepper. Set aside.
Combine remaining salt and white pepper, flour and sichuan pepper in a wide shallow bowl. Heat oil in a wok on high, until a cube of bread sizzles on contact. Holding prawns by tail, dip into egg then into salt mixture. Deep-fry for 2-3 minutes until golden. Drain on paper towel. Continue with remaining prawns.
Serve immediately garnished with coriander sprigs along with dipping sauce.