fairy butter
/ˌfɛːri ˈbʌtə/noun
1A jelly- or butter-like substance of natural origin: (a) any of several yellow or white jelly-like fungi; especially yellow brain fungus, Tremella mesenterica.
2 Cookery. Butter mixed with sugar and other ingredients, typically eggs, flower-water, and almonds, served as a spread or to accompany a dessert. Now chiefly historical.
Origin
Early 18th century; earliest use found in Charles Leigh (1622–?1701). In some forms from the genitive plural of fairy + butter. In some forms from fairy + butter. In some forms from the genitive of fairy + butter.