Rinse elderberries and strip with a fork from the stems. Boil apple juice and 800ml water with lemon zest and spices in a pot. Peel apples and pear, remove the cores and cut fruit into wedges. Cook with berries 20 minutes in boiling liquid. Drain in a colander, press pulp with a spoon and collect the juice. Again bring to a boil, add the sugar. mix 2 tablespoons cornstarch with a little water and thicken the soup with it. Season with lemon juice.
For the topping beat the egg whites with the sugar and salt until very stiff. Fill a wide, shallow pan with a few inches of water and bring to a boil. Scoop ovals with two spoons from the white mixture and slide into the water. Poach on each side 4 minutes. Pour the soup into plates and top with the ovals.