Put the rice in a medium saucepan. Add 2 cups water, set the saucepan over high heat, and bring it to a boil.

When the water boils, stir the rice once, cover the saucepan, and lower the heat to low. Cook for 15 minutes.

Take the saucepan off the heat and let the rice sit, still covered, while you make the stir-fry.

Set the tofu cubes on a plate lined with a clean towel or paper towels. Press gently so the towel absorbs extra moisture from the surface.

Put the tofu in a medium bowl. Sprinkle the remaining 1 tablespoon cornstarch over the tofu and toss gently until the cubes have a light, even coating.

Heat 2 tablespoons of the oil in a large nonstick skillet or wok over medium-high heat.

Add the tofu to the skillet in one layer. Cook without moving it for 3 to 4 minutes, until the bottom side is golden.

Turn the tofu pieces with tongs or a spatula. Cook for 3 to 4 minutes more, turning once or twice, until most sides are golden and the tofu looks a little firmer.

Transfer the tofu from the skillet to a plate.

Add the remaining 1 tablespoon oil to the same skillet. Add the carrots and the scallion whites, and cook over medium-high heat for 2 minutes, stirring often.

Add the chopped bok choy stems to the skillet. Cook for 2 minutes, stirring, until they start to soften but still look bright.