The appetizing gloss and snap of your favourite chocolate bar is the result of tempering. Tempering is the process of heating and cooling chocolate in a way that not only makes it shiny and gives it that satisfying snap when you break it, but also preserves it and raises its melting temperature so that it doesn't melt too quickly when you hold it in your hands. Not all chocolate needs tempering. There's no benefit, for example, to tempering chocolate that you'll use for baking or hot cocoa. Temper chocolate that you'll mould, eat out of hand or use as a coating or dip.
Cut the chocolate into small pieces using the knife.
Add two-thirds of the chocolate to the bowl. Set the bowl over the pot of water. Pour off some water, if necessary, so that the bowl sits above it, not in it.
Melt the chocolate over simmering, not boiling, water. Stir it constantly with the wooden spoon as it melts. Insert the thermometer into the chocolate as soon as it has melted. Heat the melted chocolate to 110 to 115F.
Add the rest of the chocolate to the bowl. Stir until it has melted. Remove the bowl from the pot. Allow the chocolate to cool to 80 to 82F.
Return the bowl to the pot and reheat the water until it simmers, stirring constantly. Reheat the chocolate until it reaches 87 to 91F. Remove the bowl from the pot. The chocolate is ready for use.
An alternate method of cooling the 100 to 115F chocolate is to pour it onto marble or laminate surface and scrape it back and forth with a spatula until the temperate lowers to 80 to 82F.
Water or other liquid mixing with the chocolate will cause it to clump. Chocolate can scorch if heated to 130F or more.