Method: Blend the shelled prawns into paste and mix in the seasoning, marinate for about 15 mins. Wipe shiitake mushrooms with a slightly damp paper towel and discard the stems. Bring a pot of water to the boil (add little oil and salt into it) and blanch baby boy choy for about 3 minutes. Dish and drain. Sprinkle some corn flour on mushrooms then stuff with prawn paste and steam until cooked through (about 10-12 mins). Transfer steamed stuffed mushrooms onto serving plate and garnish with baby boy choy. Heat sauce mixture to boil and pour over the stuffed mushrooms. Serve immediately.