If ease and a smooth and shiny chocolate shell appearance matter to you, melting discs are the way to go. Ghiradelli and Merkens are both great and very popular. If you have a chocolate bar that you love to use, make sure to roughly chop it before microwaving it with coconut oil. Chopped chocolate will take less time to melt than a solid bar. Chocolate chips are designed to not melt, so they will take longer to melt in the microwave. They may also result in a streaky appearance in the chocolate. It is best to use coconut oil when melting if you plan to use chocolate chips.