Grind together grated ginger, pepper, and salt, then mix with water.
In a glass bowl toss together the plantain cubes and spice mixture.
In a deep skillet, heat oil (just deep enough to allow plantains to float) to 175°C. Fry plantains, turning once, until golden brown on both sides. (Don't try to fry them all at once; they should not touch each other while frying).
Drain on absorbent paper, keep in warmed oven until all the plantains are fried. Serve kelewele immediately.