Best way to melt down chocolate to add to Irish cream to drink?

Basically, I want to make chocolate Irish cream . I buy a Baileys equivalent which costs me £4 in a different brand, but I have a bit of a sweet tooth and want to try a chocolate Irish cream but the £19 tag is a bit steep for me. If I want to add chocolate to a store bought Irish cream, would the best method be to heat milk in a pan, add the chocolate, leave to cool, then mix? Would anyone recommend another method for better results? http://www.reddit.com/r/cocktails/comments/3f0kbv/best_way_to_melt_down_chocolate_to_add_to_irish/