emulsion [ih-muhl-shuhn] noun
A mixture of two liquids that, without the proper technique, will not readily combine, such as oil and water. An emulsion is produced by slowly adding one product to the other while rapidly combining them. This suspends one ingredient within the other. The result is usually thick, glossy and creamy in appearance and texture.
Common examples of emulsions include hollandaise sauce, mayonnaise and vinaigrettes, and in the sweet kitchen, ganache is probably the most common.
Ganache has a tendency to “break,” at which point it will look separated. Sometimes the chocolate will look lumpy or grainy and there will be an accompanying fatty oil slick. This means the ganache was not prepared properly or that the types of ingredients used, or the ratio of ingredients, prevented an emulsion from being created. Just as with mayonnaise, the use of a blender, food processor or stick blender can bring the ingredients together forcefully enough to aid in the creation of a proper emulsion. If your ganache has “broken,” try zapping it with a hand blender to bring the ingredients together into a silky emulsion, perhaps drizzling in some cold cream as you go.