Hardtack:
2 cups of flour or more, as the maker so desires.
Enough water so that the mixture is not watery but paste like
Bake at 350-400 degrees Fahrenheit in a stove, grill, or on a cooking stone until it becomes hard, or at least cooked enough that a toothpick doesn't bring back spare parts (can be 10-15 min or more depending on how much). (Butter or oil can be put down to grease any pots and pans)
For dessert version:
About halfway through baking or as soon as its out of the cooking stage smear a fourth to a half a stick of butter all over it.
After the butter is on, sprinkle sugar to the desired coating.

Either way it is quite delicious. And it, of course, keeps extremely well. If left so that it becomes quite hard just have a cup of coffee or tea with it.