Put the egg white in a bowl with the potato or cornflour. Whisk together to a fine batter. Season with sea salt and ground white pepper and mix. Add the prawns and coat well.

Heat a wok or saucepan just less than half-full with groundnut oil, heat to 180C checking with a cooking thermometer. Lower the prawns into the oil using a spider strainer and fry for less than 10 seconds. Scoop out and drain on a plate lined with kitchen paper.

Boil the kettle, place 1 tbsp Longjing tea in a bowl and pour over 150ml hot water. Let it steep for 2 mins.

Add 1 tbsp oil to another wok or deep frying pan and put over a high heat until the oil is slight smoking. Add the prawns and 50ml of the tea, followed by the spring onions, shaoxing rice wine or dry sherry, add a few tea leaf pieces and season with salt and ground white pepper, then stir in the cornflour mixture to thicken. Add a little more tea or water if you need to. Take off the heat and serve immediately with cooked jasmine rice and other Chinese dishes.