"Drinking chocolate" as the base for chocolate fudge? Huh? I always used good quality semi-sweet chocolate chips. Works for me.
I will say that my candy always, always turns out better when I make it on a cold, clear night with low humidity. Something about the moisture in the air can affect the way the fudge "comes set." Sometimes it won't set, or it will be grainy.
@Grivusangel -- So right about that white vanilla flavoring! Yuck! My mom bought some from the ladies' group at church years ago and it was awful. It was a good brand, but the white stuff just tastes bad. I don't mind beige vanilla fudge. If you make it with marshmallow creme, that can make it whiter.