I tried this for the miss, and I can give our perception on how it worked. (Well, it was the old recipe you thought-created, I can go back to find the other one; This one is chocolate-only).
I'll just say that even though peppermint is strong, it can be a bit overwhelmed by chocolate, if you do want peppermint to be the star. However, we were looking for a very specific clone of a juice, where peppermint is the primary, and chocolate is a nice secondary taste (almost aftertaste).
The recipe you gave me to try had around 8:1 chocolate to peppermint. I'd probably try 4:1 next time, and see how that goes.
The "Chocolate" (not milk, but it is clearly a milk chocolate) really sweetened up the mix a lot. If you're looking for a darker chocolate, you might want a really low percentage of milk, or possibly skip altogether (which is blasphemy, I know!).
I never got around to making a 2nd tweaked batch, but it's going to happen soon, with all this new free-time I keep fantasizing about

Bill really did give me all the tools needed to customize and create exactly what I'm looking for, it's just up to me to actually do it!