Here's what happened next:
Dropped a overflowing tablespoon or so of liqueur into a bowl. (I used triple sec, but I think this should work equally interestingly with almost anything.)
Gently nuked it until it was hot enough to melt chocolate.
Dropped in a single square of the darkest chocolate I had on hand (in my case, the nicely priced 80% chocolate noir bars from Costco).
Stirred, melted, adjusted for consistency.
Results: die-for chocolate sundae sauce! So good, I decided right then I had to get the word out.
You might find you need to nuke a bit more if the chocolate doesn't melt the first time. Just be conservative, because the chocolate will start to re-congeal if it's heated too long.

