Melt the chocolate in a double boiler or put the chocolate pieces in a metal bowl and place it over a saucepan of simmering water. This prevents the chocolate from burning (which can easily happen over a direct flame). Adding vegetable shortening (such as Crisco) helps keep the chocolate liquidy and gives it extra sheen but is not necessary. The chocolate will melt slowly, so leave it alone (no need to stir) and watch carefully. Once the chocolate is completely melted, you can use it as a dip or drizzle it over the cookies.