Light Dortmund Beer Soup (Dortmunder Bier Suppe)

["Rub the sugar lumps over the surface of the lemon.", "Bring the beer to the boil with the cinnamon stick, cloves and sugar lumps.", "Add a pinch of salt.", "Blend the cornflour with a little water (1/4 cup) and add it to the soup, to thicken it.", "When soup has thickened, turn the heat down very low, wait a few minutes, and then whisk in the 4 beaten egg yolks.", "DO NOT reboil the soup or the yolks will curdle.", "Keep the soup on a very slow simmer while preparing the""snow dumplings"".", "Whisk the egg whites with 1 Tablespoon of sugar""to a very stiff snow"" (stiff enough to hold shape, but not dry).", "Into a pan of simmering water, drop spoonfuls of the snow and allow them to set (like a dumpling).", "When set, remove from pan with a slotted spoon.", "Remove cinnamon stick from soup, and ladle into bowls.", "The""snow dumplings"" are then placed on top of the soup and sprinkled with a bit of cinnamon sugar."]