Chocolate needs to be re-tempered after melting to make sure you have a chocolate that doesn’t soften at room temperature or fall apart when filled or molded. There are several methods of tempering chocolate. I’m giving you the simplest.
To Temper Dark Chocolate: Chop the chocolate. Heat half of it in the top half of a double boiler over barely simmering water. Stirring until the chocolate’s temperature reads between 115 and 120 degrees on a candy thermometer (the chocolate will melt quickly, and the temperature may already be high enough, even before all the chocolate is melted). Remove the saucepan from the heat and stir until the chocolate is melted through and smooth. Add the rest of the chocolate in batches until it is all incorporated. Adding the chocolate in this method will “seed” the chocolate with crystals and make sure it tempers correctly. Stir continually. When the chocolate starts to thicken check the temperature again. You will want it to be cooler than 90 degrees before you stop stirring. At this point it is tempered and you can use it as such.
To test whether it’s tempered you can dip a knife into it and put it in the fridge for a few minutes. The sample should harden well.
Milk chocolate and white chocolate tempers at between 86 and 88 degrees.