Malted Milkshake

Malted milk powder — dried milk blended with malted barley and wheat — was patented in 1887 by William Horlick in Racine, Wisconsin, originally marketed as an easily digestible food for infants and invalids. The leap to the soda fountain is credited to Ivar 'Pop' Coulson, a worker at a Walgreens drugstore in Chicago, who is said to have added scoops of ice cream to the existing milk-and-malt drink around 1922, creating the thick malted milkshake that became a national fountain craze. Both anchoring facts — Horlick's Racine patent and the drink's Chicago-area popularization — place the malt firmly in the upper Midwest. The 'malt shop' became shorthand for a whole era of American soda-fountain culture.

Thick and cold, with the clean sweetness of an ice-cream shake deepened by malt's toasty, biscuity, almost cereal-like flavor and a faint savory edge. The malt powder gives it a slightly thicker, grainier body than a plain shake, and the finish is warm and nutty rather than sugar-flat. With chocolate it tastes like a frozen malted-chocolate candy; with vanilla, like toasted cereal cream.

The defining ingredient is malted-milk powder, made from barley that has been germinated and dried so its enzymes convert starches into maltose, then dried with milk solids and wheat flour; that malting is what gives the toasty, complex flavor and the soluble malt sugars. Blended into a shake it both flavors and thickens, its starches and proteins binding water and adding body. The shake itself is an emulsion of butterfat, air, and ice from the ice cream: blending shears the ice cream fine and whips in air for a thick, aerated, scoopable-but-pourable texture, while just enough cold milk loosens it to drink through a straw. Keeping everything very cold preserves the thick, frozen body.