Chocolate melts best at temperatures between 104 and 113 degrees F (40 degrees C and 45 degrees C). Never melt chocolate directly over a heat source. Use an indirect source like a hot water bath.
Tempering determines the final gloss, hardness, and contraction of the chocolate. When you melt chocolate, the molecules of fat separate. To put them back together, you temper it. There are a variety of ways to do it. One of the easiest ways is to place it in the microwave for 30 seconds at a time on high power until the chocolate is melted. Be very careful not to overheat it. The chocolate will not look as if it has melted because it retains its shape. It should be only slightly warmer than your bottom lip. You may still see lumps in it, but don't worry; the residual heat of the chocolate will melt them. You can also use an immersion blender to break the lumps and start the recrystallization process.
Usually, the chocolate begins to set (recrystallize) along the side of the bowl. As it begins to crystallize, mix those crystals into the melted chocolate and they will begin recrystallization process. I like to use a glass bowl because it retains the heat and keeps the chocolate tempered for a long time.
Another way to temper chocolate is called seeding. In this method, tempering is achieved by adding small pieces of unmelted chocolate to melted chocolate. The amount of unmelted chocolate to be added depends on the temperature of the melted chocolate but is usually one fourth of the total amount. I usually use an immersion blender to mix the two together.
The classic way to temper chocolate is called tabliering. Chocolate is melted over hot water bath to a temperature between 88 degrees F and 90 degrees F (31 degrees C and 32 degrees C). (White and milk chocolate are melted to a temperature approximately 2 degrees F less, depending on the amount of milk fat they contain.) Two thirds of the melted chocolate is poured on a cold table marble surface. The chocolate is spread out and worked with a spatula until the temperature of the chocolate is approximately 81 degrees F (27 degrees C). At this stage, it is thick and begins to set. This tempered chocolate is then added to the remaining one third of nontempered chocolate and mixed thoroughly until the mass in the bowl has a completely uniform temperature. If the temperature is still too high, part of the chocolate is further worked on the cold table until the correct temperature is reached. This is a lot of work, requires a lot of room, and makes a big mess.
A simple method to check tempering is to apply a small quantity of chocolate to a piece of paper or to the point of a knife. If the chocolate has been tempered correctly, it will harden evenly and show a good gloss within 5 minutes.
Chocolate is susceptible to moisture and absorbs external odors. It is also important to protect it from light and air. Store it in a cool, dry place in closed packaging. The ideal temperature for storing chocolate is between 54 degrees F and 68 degrees F, (12 C and 20C). Do not store chocolate in the refrigerator, where the humidity (moisture) will affect it.
Recipe Courtesy of Jacques Torres, Exec. Pastry Chef, Le Cirque 2000 and Author of Dessert Circus At Home