Peel and wash the carrots and potatoes. Cut carrots into slices and potatoes into cubes. Clean, wash and chop the beans, mangetouts and cauliflower. Peas peel.
Clean, wash and roughly chop the spinach. Bring a litre of salt water to the boil. Cook the carrots, cauliflower and potatoes for ten minutes. Add peas, mangetouts, spinach and prawns. Mix three tablespoons of milk with flour.
Pour the remaining milk into the vegetables and bring to the boil. Season with salt, pepper, butter and sugar. Bind with the flour mixture, bring to the boil again and simmer for five minutes. Wash parsley, dab dry, chop coarsely.
Arrange the soup in a terrine and sprinkle with parsley.