[larsdangly]

I don't think there is any basis for calling it two separate attacks; the language says your damage is doubled, and the rules go out of their way to have multiple attacks per turn be an exceptional situation that is always commented on. I think it is clear you are supposed to do your HTH attack as normal but do twice as much damage. I don't think it matters very much whether you double the dice or roll once and double; I would do the former, but if you did the latter it wouldn't be game breaking