Tempering is a technique that serves two different purposes. Tempering chocolate is a process where through heating and cooling of the chocolate, stabilized crystals are formed. These stabilized crystals allow the chocolate to be glossy and remain firm at room temperature. Eggs and other dairy products are tempered so that they can be incorporated into a hot liquid without cooking or curdling.
To temper chocolate, gently melt in a double boiler over low heat. Using a candy thermometer, cool the chocolate down to a very precise temperature. Dark chocolate should be between 88-89ºF (31ºC). Milk and white chocolate should be between 84-86ºF (29-30ºC). Another (easier) way to temper chocolate is to melt down part of it and then add in the remaining solid chocolate. Stir constantly until it is completely melted and smooth.
To temper eggs and dairy, add a small amount of the hot liquid to the cold dairy or eggs and whisk together until combined. This will slowly raise the temperature of the cold ingredients making it possible to combine them with the hot liquid without curdling. Add the warmed whisked mixture to the remaining hot liquid and combine.