Grappa is made from the “pomace” left over after winemaking has taken what it needs from grapes and discarded all the other bits: skins and nubs and twigs and such. It doesn’t taste much of grapes specifically, but it does have a comforting woody character that nicely cuts through sweet spirits and helps to reveal flavors that otherwise get lost under less-subtle flavors.
Simon Difford’s Italian Milk Punch is an excellent case study of this utility: even this small measure of grappa adds a drying woody note that exposes herbal, complex notes in amaretto and Galliano that are difficult to detect when they appear in the more typically sweet cocktails they usually show up in. This is a dessert cocktail for someone who doesn’t like dessert.
