Yellowman

yellowman is an Irish toffee confection made of butter, brown sugar, vinegar, and golden syrup. These ingredients are melted and boiled at a temperature of 285 °C (545 °F). At this stage a quantity of sodium bicarbonate is added to the liquid causing it to foam spontaneously. This additional ingredient gives the confection its characteristic brittle and honeycombed texture. Production of the confection probably dates to the early 19th century when sodium bicarbonate was first introduced into Ireland.