Wash the meat, dab dry and cut into pieces. Mix starch and soy sauce and marinate the meat in it for about 15 minutes. Meanwhile peel and finely chop the onion. Clean the mushrooms, wash if necessary and cut in half.
Clean, wash and cut the leek into rings. Drain the pineapple on a sieve. Collect the juice. Cut the pineapple into pieces. Drain the meat. Collect the marinade. Heat the oil in a pan and fry the meat for about 5 minutes.
Season with salt and pepper. Add onion, leek, mushrooms and pineapple and fry for another 5 minutes. Deglaze with stock and marinade and bring to the boil. Add 5-6 tablespoons pineapple juice, lemon juice, vinegar and ketchup and season with soy sauce, sugar, sherry, Chinese spice and paprika.
Wash the tomato, quarter it, remove the seeds and cut into small cubes. Sprinkle over the pan and serve garnished with parsley as desired.