Defrost the prawns if necessary. Wash the shrimps. Boil up broth or fish stock. Add 2 portions of prawns to the stock, bring to the boil and remove with a skimmer. Put the stock and prawns aside.
Peel and finely dice the onions and ginger. Peel garlic and cut into slices. Clean the chilli, cut lengthwise, remove seeds, wash and dice very finely. Fry garlic in hot oil and remove.
Sauté onions, ginger and chili in beard fat at medium heat for about 5 minutes. Dust with curry and flour and sauté briefly. Stir in the stock little by little and bring to the boil while stirring.
Stir in coconut milk. Clean lemon grass, cut in half lengthwise, crush and add to the curry. Simmer covered at low heat for about 15 minutes, stirring occasionally. Clean and wash the spring onions and cut them into fine rings.
Season curry with salt, pepper, coriander and lemon juice. Remove the lemongrass. Heat prawns and 3/4 of the spring onions in the curry. Season curry to taste again. Serve everything. Garnish with the rest of the spring onions and coriander green.
Sprinkle garlic over the curry. Basmati rice tastes good with it.