Grind ginger, garlic, green onions and green chillies to a paste in a mortar and pestle. Set aside.
In a saucepan over a medium heat, reduce the chicken stock and soy sauce to 2 cups - this will take 10- 15 minutes.
When that's done, season with white pepper and add sesame oil. Thicken with cornflour that has been dissolved in the water.
Lightly coat the prawns in flour - shake them in a bag with the 1/2 cup flour. Heat the peanut oil until it's very hot, then add the prawns.
Cook the prawns 2-3 minutes in the hot oil and add the capsicums and onion, cook for another minute. Don't over-cook.
Drain the oil from the prawns and vegetables, then return them to the wok. Add the garlic-ginger paste and cook until lightly browned. Finish with a splash or two of white wine if desired - stir it through, then serve with rice.