Knead beef with onions, wine, 2 tbsp soy sauce, egg yolk and salt. Make small balls, roll them in flour and fry them. Then boil them with pineapple juice and cut pineapple. Separately, mix 1 tbsp soy sauce, vinegar, sugar and 2 tbsp flour. Mix well and add to the dish. Simmer 10 minutes and serve, garnished with feathers of green onions.