A sauce made of butter, mustard, cream and vinegar
Nathaniel Gubbins, an alias of Edward Spencer, wrote Cakes & Ale in 1913 and invented many spicy dishes and sauces, including Gubbins Sauce which became well known in Britain. In Cakes & Ale the instructions to make the sauce are as follows:
Melt on the plate a lump of butter the size of a large walnut. Stir into it, when melted, two teaspoonfuls of made mustard, then a dessert-spoonful of vinegar, half that quantity of tarragon vinegar, and a tablespoonful of cream—Devonshire or English. Season with salt, black pepper, and cayenne, according to the (presumed) tastes and requirements of the breakfasters.