Ooooooooooohhhh... I'd cut Paarthy into steaks and make travel jerky out of his tail. Paarthy is pretty much a wimp so I imagine his cutlets would be tender and juicy. Like a big, plump turkey sitting on a mountain. I could get behind a mod like that. Me and the Blades would be eatin' good for months. I imagine using the Shout he taught me to put a nice sear on him before I slow cook him. Sounds like a party.
More on topic, it's only cannibalism if you are eating someone/something of the same species. Correct?
You could argue a Dragonborn is a dragon.
I've never read anything indicating that the Dragonborn had actual dragon blood. As far as I know, the Dragonborn has the soul of a dragon and nothing more. If you know of some lore that speaks of the Dragonborn having actual dragon blood, I'd be very interested in the link.
If he has dragon blood, then I'd say yea, that could be viewed as cannibalism. But if not and he just has the soul of a dragon then definitely not imo. Cannibalism is all about flesh and bones and has nothing to do with devouring the soul... which the Dragonborn happens to do on a regular basis anyway come to think of it. So we are already performing spiritual cannibalism anyway, may as well enjoy a good meal too.