Chocolate pairs well with a wide variety of flavors. Vanilla, of course, is the most common, and many candy manufacturers add either pure vanilla or vanillin (an artificial vanilla flavor) to their chocolate candies, since our palates have become accustomed to chocolate with a light vanilla undertone.
Chocolate can be flavored with alcohol-based extracts, liqueurs, or flavored oils. Alcohol-based extracts are commonly found in the baking aisle of grocery stores and include flavors like vanilla, almond, hazelnut, coconut, and lemon. Liqueurs and spirits that pair well with chocolate include amaretto, brandy, rum, Cointreau, Grand Marnier, and Kahlua. The important thing to remember about adding alcohol extracts and liqueurs is that these liquids need to be added to chocolatemixtures, not pure melted chocolate, otherwise the alcohol will cause the chocolate to seize and form a lumpy mass. These flavorings are well-suited for ganache mixtures or other candies that involve mixing melted chocolate with cream, milk, or other substances.
Oil-based flavorings, sometimes called “candy flavoring,” can be added directly to melted chocolate without causing it to seize. Common oil-based flavorings include mint, cherry, strawberry, hazelnut, cinnamon, and orange. Many of these flavorings are potent—especially mint—and should be used more sparingly than their alcohol-based counterparts. Oil-based flavorings can be found at some specialty cooking stores, craft stores, and online confectionery retailers.