Cut the bean curd into 3-cm (1 -in) squares.
Clean the leek and cut into 3-cm (1 - in) pieces.
Heat 1 1/2 tablespoons of oil and stir-fry the bean curd for 1 minute.
Add the leek and stir-fry for another minute.
Add 3 tablespoons of water and the soy sauce to the pan and simmer until the leek is tender.
Season with salt and pepper and serve.