Pick, wash, and chop fine a very large handful of chervil. Melt a piece of butter the size of an egg with two tablespoonfuls of good flour. Stir smooth. Do not let it colour at all; then add the chervil and let it simmer ten minutes, stirring well. Pour on it sufficient stock or water (water is quite as good as stock, in my opinion) to make the soup (rather less than more, as one can easily add a drop if too thick). Let it boil half an hour. Just before serving the soup put the yolks of two fresh eggs, one teacupful of milk or cream and a bit of sweet butter, well mixed together and beaten up, into the soup tureen; pour the boiling soup into this thickening, stirring it well till mixed. The same receipt exactly applies to sorrel Soup.