Chocolate expert Alice Medrich points out that putting a metal bowlful of chopped chocolate in a wide skillet of very hot but not simmering water is better than suspending it over a pot of barely simmering water, double-boiler style, for a very good reason. In a double-boiler setup, you can’t see what’s going on with the water and it can easily start boiling since it’s covered by the bowl of chocolate. Steam is hotter than boiling water, and it can scorch the chocolate if you’re not careful. With a bowl of chocolate heating in a few inches of water in a wide skillet, you can see what the water is doing and control the temperature as needed.
Though you might find it fussier than using a water bath, the microwave is also a good tool for melting chocolate. Heat the chocolate on 50% (medium) power for 1 minute and then stir. Continue heating in 15 second intervals, stirring between each interval, until the chocolate melt
Tips for melting chocolate
Chop white and milk chocolate finely. White and milk chocolates are delicate; if they get too hot they can get gritty or scorch. Chopping them finely and stirring frequently helps melt them quickly and evenly with minimal heat.
Chop dark chocolate coarsely. It’s more forgiving than white or milk chocolate, so chop it into coarse almond-size pieces. It’ll take a little longer to melt than if it were finely chopped, but it means less knife work up front, and less frequent stirring.
Watch out for water. Unless you’re melting chocolate along with a significant amount of water or another ingredient like butter or cream, just a few drops of water (like what might be in a wet bowl) can make the chocolate seize into an unworkable mass. Be sure that all the tools that come in contact with the chocolate are bone-dry before you start, and don’t cover melting chocolate (condensation from the lid might drip into the chocolate).