Peel the eggs and carefully prick them on all sides with a toothpick. Pour the soy sauce into a small (no more than 22 cm in diameter) saucepan with a thick bottom and bring to a boil over medium heat.
Place the eggs in the sauce and cook, lowering the heat slightly, turning constantly, until the eggs are brown and the sauce has thickened, 3 to 5 minutes.
Remove the eggs from the sauce, transfer to a plate and set aside. Serve with boiled rice or use in sandwiches.