Warm the rice according to the package directions, or microwave leftover rice until hot. Cover it to keep it warm.

Pat the tofu dry with paper towels. Cut it into 1-inch cubes.

Put the cornstarch, 1/2 teaspoon of the salt, and 1/2 teaspoon of the black pepper in a medium bowl. Stir to mix.

Add the tofu to the bowl and toss gently until the pieces are lightly coated on all sides.

Add 2 tablespoons of the oil to the hot skillet and swirl to coat the bottom.

Put the tofu into the skillet in a single layer. Cook for 4 minutes, leaving it mostly undisturbed, until the bottom sides are golden.

Turn the tofu pieces with tongs or a thin spatula. Cook for 3 to 4 minutes more, until several sides are crisp and golden. Transfer the tofu to a plate.

Add the remaining 1 tablespoon of oil to the same skillet. Put the green beans into the skillet and spread them out.

Cook the green beans for 5 to 6 minutes, stirring every minute or so, until they are bright green with browned blistered spots and are just tender.

Add the scallion whites and the jalapeño to the skillet. Stir for 1 minute, until they soften slightly.

Add the garlic, the remaining 1/2 teaspoon salt, and the remaining 1/2 teaspoon black pepper to the skillet. Stir for about 30 seconds, just until the garlic smells fragrant.