Get the tofu ready: Set a large nonstick skillet, a small bowl, and a plate by the stove. Wrap the tofu in a clean towel or paper towels and press it under a heavy pan or a few cans for 10 minutes.

While the tofu presses, cut the broccoli into bite-size florets, slice the bell pepper, halve the baby corn lengthwise, slice the scallions, and keep the scallion whites and greens in separate piles.

Put the pressed tofu cubes into a medium bowl. Sprinkle 1 tablespoon of the cornstarch over the tofu and toss gently until the cubes have a light, dry coating.

Mix the sauce: In the small bowl, stir together the remaining 1 tablespoon cornstarch, the black bean garlic sauce, soy sauce, brown sugar, and water until smooth.

Brown the tofu: Place the skillet over medium-high heat and add 1 tablespoon of the oil. When the oil looks shiny, add the tofu in one layer.

Cook the tofu for 3 to 4 minutes, without moving it much, until the bottoms look golden brown.

Turn the tofu pieces with tongs or a thin spatula. Cook for 3 to 4 minutes more, until several sides are browned and the edges look a little crisp.

Transfer the tofu from the skillet to the plate and keep it nearby.

Cook the vegetables: Add the remaining 1 tablespoon oil to the same skillet. Put the broccoli into the skillet and cook for 2 minutes, stirring often, until it turns bright green.

Add the bell pepper, baby corn, scallion whites, and garlic to the skillet. Cook for 3 to 4 minutes, stirring often, until the pepper softens at the edges and the broccoli is tender but still has some bite.

Stir the sauce in the bowl again so the cornstarch is fully mixed in. Pour the sauce into the skillet with the vegetables.

Finish the stir-fry: Cook the sauce for 1 to 2 minutes, stirring often, until it bubbles and thickens enough to lightly coat the vegetables.