Shell and de-vein the prawns, wash them thoroughly. Drain and keep aside. Peel and finely chop the onion. Peel and crush the garlic. Wash, peel and chop the potatoes. Clean, wash and chop the parsley. Melt butter gently over low heat in a heavy bottomed saucepan.
Add the chopped onions and crushed garlic and fry till onions become soft. Add the potatoes and fry for 2-3 minutes. Add the fish stock . simmer for 2-3 minutes.
Stir in half the prawns, cook for 2-3 minutes and remove from heat. Allow to cool slightly. Puree the soup in a blender or food processor and pour back into the saucepan. Add cream, salt and pepper. Simmer gently for 5 minutes. Stir in the parsley and the reserved prawns, cook till done. Remove from heat and serve hot.