variation on above recipe:
Add the peanut butter to the saucepan/pot at the same time as the chocolate and cocoa. It should melt into the mixture providing a thicker blend with more body and a huge flavor.
I made this one time when I went through an experimental food period (what can I do to make this more exciting?) and I like it so much that regular hot chocolate just seems bland by comparison.
Postscript: You can use more peanut butter if you like, but I found that using more than 3 spoonfuls causes it to not melt as easily.