Heat 1 tablespoon of the oil in a saucepan. Add the roughly chopped spring onions, garlic and thyme leaves and fry over a gentle heat until soft. Add the beans, stock and cream. Bring the soup to the boil, then reduce the heat and simmer for 5 minutes.
Transfer the soup to a liquidizer or food processor and blend until smooth. If it is a little thick, add a little more cream or stock. Season the soup with salt and pepper.
Place a frying pan over a high heat and add the remaining oil. Season the prawns with salt and pepper, then fry them in the pan for 4 minutes, or until they turn pink.
Stack the prawns in the centre of 4 bowls and pour the soup around them. Garnish the dish with a few chopped spring onions and the chives.