Step 1: Finely chop all of the chocolate into small, even pieces with a serrated knife. You can skip this step if you are using discs of couverture chocolate rather than bars.

Step 2: Bring a pot with about an inch of water to a gentle simmer (do not let it come to a boil). Place your double boiler on top, or if you don't have one, use a large metal or glass bowl. Do not let the bottom of the bowl touch the water (the chocolate will overheat).

Step 3: Add three-fourths of your chocolate into the double boiler. Keeping a constant eye on the chocolate, allow it to gradually melt while stirring slowly and continuously with a rubber spatula. Check the temperature often.

Melt until the chocolate has reached a temperature of 113°F / 45°C. Be careful to not exceed this as white chocolate will easily scorch over this temperature.

Step 4: Once the chocolate has fully melted, remove the double boiler from the heat and set it on a heat-safe surface. Carefully wipe any moisture from the bowl to eliminate the risk of water getting into the chocolate (see chocolate seize in problems you may encounter). Keep the pot heated as you will need it again soon.

Step 5: Add in the remaining fourth of chopped chocolate, a little bit at a time. Stir constantly and allow it to melt before adding more. Keep an eye on the temperature.

Cool until the temperature of the white chocolate is 80.6°F / 27°C.

If the chocolate is warmer, keep stirring until the temperature lowers to this. Be patient as it may take some time, especially if working with a large quantity of chocolate. If the chocolate reaches this temperature and there are still unmelted bits, remove them. If you leave them in, the chocolate will over crystallize and become sticky.

Step 6: Return the double boiler to the simmering pot. Stir while reheating the chocolate. Reheat the white chocolate to its working temperature of 82.4-84.2°F / 28-29°C.

You want to keep the temperature as close to this as possible. Do not exceed 88.7°F / 31.5°C or the white chocolate will lose its temper. (If you accidentally do, return to step 3.) Remove the bowl from the heat and carefully wipe away any condensation.

Step 7: Test to see if your chocolate is in temper (see 'how to test temper'). If the chocolate fails the test, simply return to step 3 to re-temper the chocolate. Once your chocolate is ready, remember to keep it in temper as you are working with it.