By Harold McGee
Fruit curds—lemon curd is the most common—can be thought of as a kind of cream in which the place of milk is taken by fruit juice, usually enriched with butter. (They may have begun as a sweetened version of creamy eggs scrambled with fruit juice.) Fruit curds are meant to have a spoonable consistency that works well as a filling for small pastries or a breakfast spread, and must be sweet enough to balance the acidity of the juice. They therefore contain no flour, more sugar, and more eggs than do milk creams, typically 4 eggs (or 8 yolks) and a cup or more of sugar for a half-cup of butter and a half-cup of juice (375 gm sugar per 125 ml each of butter and juice).