Clean prawns, remove legs and devein, but leave shells and heads intact. Cut spring onions to 3" section, reserve about 1 tablespoon of chopped white part only. Lightly crush the rest of the 3" white part using the side of the knife and put aside together with the greens. Marinate prawns with oyster sauce, pinch of white pepper powder, pinch of salt and keep aside for 30 minutes. Heat oil in saucepan and fry prawns in a single layer on both sides about 2-3 minutes each side until brown and shell turns crispy. Remove and keep aside. Keep marinated juice from the prawn marinade to be used later. In a clean saucepan, heat 1 tablespoon oil. Saute chopped garlic, chopped ginger and chopped spring onions, until fragrant and light brown. Add in retained marinated juice, 2-3 tablespoon of water, stir till it boils and add in the prawns along with the spring onions. Stir for about a minute and add salt if necessary. Add in the Chinese cooking wine, give a quick stir, dish out to a serving plate and serve hot. Enjoy!