Preheat the oven to 350°F. In a small bowl, combine the flours, baking powder, and salt. Using an electric mixer, blend the peanut butter, butter, and vanilla in a large bowl.
Add the sugars and blend, then add half the flour mixture and blend again. Add the egg and water and blend, then add the remaining flour mixture and blend again.
Form the dough into one large mound with your hands, then gently roll the dough into 30 small balls, about 1 rounded tablespoon dough each.
Arrange the dough balls on parchment paper-lined baking sheets about 2 inches apart. Using the back of a fork, flatten the dough balls in a crosshatch design. Bake the cookies 22 minutes or until crisp. Cool cookies on the baking sheets for 5 minutes. Transfer cookies to racks and cool completely.