Preheat the oven to 350ºF. Prepare an 8 x 8 baking pan by oiling the bottom and sides.
Grind the pepper (See Kitchen Notes).
Into a large heatproof bowl, sift the flour, baking soda, ginger, cinnamon, five-spice powder, pepper and salt.
Break the egg into a separate medium bowl; whisk the egg. Then add in the sugar, mixing until everything is an even lemon yellow. Add the vanilla and molasses and mix well (See Kitchen Notes).
Put the oil and water into a small saucepan and set it over a low flame. If it begins to boil before you are ready to use it, turn off the heat.
Pour the egg-sugar-molasses mix into the flour mix. Stir thoroughly. It will resist you and at first will seem ragged; when everything is mixed together, it will be very stiff.
When the batter is thoroughly mixed together, bring the oil-and-water to a boil (see Kitchen Notes, and I mean it) and pour it quickly and all at once into the batter. With a wooden or bamboo spoon, stir thoroughly until the batter is smooth [it may be helpful to use a whisk to accomplish this]. The batter will quickly become shiny and rather liquid.
Pour the batter into the prepared baking pan and place it straight into the preheated oven on the center rack. Set a timer for 30 minutes.
The cake is ready when a tester inserted near the center emerges with just a few crumbs on it, and it has begun to pull away from the sides very slightly.
Cool the cake in the pan on a rack. You can serve it still warm or cool. This gingerbread is so moist and intense, and the top maintains a wonderful slight stickiness.