Interesting. Very interesting. And you have all of you including me been looking at the wrong word.
The use of conundrum to mean a difficult question is, at best, quite new. Here's from one online dictionary:
1. A kind of riddle based upon some fanciful or fantastic resemblance between things quite unlike; a puzzling question, of which the answer is or involves a pun. 2. A question to which only a conjectural answer can be made.
The phrase delicious conundrum revolves around the sense of delicious I set forth above in conjunction with definition 1 above for conundrum. I have seen this occasionally over the years and had it explained to me by my father when I was a lad of very tender years. I distinctly remember, though it was almost a half century ago, the "discussion" we had about using delicious this way. I do wish I could remember what I was reading that brought the phrase to mind, but it must have been the more "modern" usage because our discussion was about the first word, not the second.
The usage quoted at the start of this thread is incorrect insofar as its use to describe a tough question. That use of the word conundrum is not reflected in my OED Compact Edition (the entire OED in reduced print format), though it is set forth in that fashion in the online Compact OED available through onelook.com.
