Mix pork with sherry, soy sauce, sesame oil, five-spice, and salt then marinate in the fridge for 20 minutes.
Heat vegetable oil to 180°C in a deep-fat fryer or heavy pan.
Dip pork into cornflour then coat in a mixture of egg and 2 tablespoons of cornflour.
Fry pork in batches until golden-brown and drain on kitchen paper.
Boil stock, soy sauce, sesame oil, vinegar, and ketchup in a pan then simmer with peppers and onions for 2 minutes.
Thicken sauce by adding a slurry of cornflour and orange juice and simmering.
Toss the fried pork into the sauce and mix well for one minute.
Fry shredded bok choi leaves for 2 minutes until crispy then season with sugar and salt.
Serve the sweet and sour pork topped with crispy seaweed alongside basmati rice.