Fruit butters are a form of preserves similar to jams, and are used in the place of preserves, jams, conserves, or marmalades. The fruit used for this purpose, which may be either large or small, is usually very ripe and somewhat soft. Therefore, as in the case of jams, imperfect fruits that are not suitable for other purposes can be used very well for butters.
Butters made from fruits differ from jams in that both the skins and seeds are always removed. The completed mixture is smooth and thick, having been made thick by long boiling and evaporation, rather than by the addition of large quantities of sugar. In fact, less sugar is used for butters proportionately than for any other preserved fruit. Spices are generally used in butters, so that the mixture is very highly flavored.
To prevent butters from scorching, they should be stirred constantly for a long period of time. This stirring becomes very tiresome, but it should not be stopped or the mixture is certain to scorch. If they are properly cooked, butters keep well with very little care in storage. Crocks are generally used for the storage of butters, but glasses or jars may be substituted.
Woman's Institute Library of Cookery, Volume 5.