Melting chocolate can be tricky, even for experienced cooks. As the cocoa butter content varies so much with different kinds of chocolate, it is extremely difficult to gauge just how long it will take to melt. If left a moment too long, or if the heat is too fierce, the mixture can easily turn into a hard, dry lump. Usually the damage will have been done and the smooth glossy consistency lost but you can try to retrieve the situation by adding butter, milk, cream or water and beating it again.
To melt chocolate break it into small pieces. Put the pieces in a completely dry heatproof bowl and set over a pan one-third filled with hot, but not boiling, water. Do not let the bowl touch the water, or the chocolate will become lumpy. Leave, uncovered, for 6–12 minutes, stirring until the chocolate is completely melted and smooth.