Drain firm tofu and press it between paper towels, pressing firmly to remove as much moisture as possible. Cut into 1-inch cubes or 1x¼-inch pieces. Toss with 1 tablespoon soy sauce and a pinch of pepper and let sit 5 minutes. Sprinkle cornstarch over the pieces and toss until each is lightly coated. Have all other ingredients ready before you start cooking.

Heat a large skillet over medium-high heat. Add 1 to 2 tablespoons of neutral oil and let it heat until shimmering before adding tofu. Add tofu in a single layer without crowding — cook in batches if needed. Let the first side cook undisturbed for 2 to 4 minutes until golden-brown, then turn and repeat on remaining sides. Total browning time is about 7 to 8 minutes. If tofu sticks, add a small drizzle of oil before flipping. Transfer browned tofu to a plate. In the same skillet, add a little oil and cook garlic and ginger over medium-high heat for about 1 minute until fragrant. Add vegetables and cook, stirring, until crisp-tender, 5 to 10 minutes. Return tofu to the pan, pour sauce over everything, and toss. Cook 1 to 2 more minutes until the sauce thickens and turns glossy.

Tofu is done when golden brown outside with a firm, chewy texture. The cornstarch coating should look set and lightly crisp, and the sauce should cling to each piece. If the sauce is thin, stir over heat for another 30 to 60 seconds — it thickens fast. Serve immediately over steamed rice with sesame seeds and scallions if using. Do not let it rest; eat right away while the crust still has texture. Key mistakes: skipping pressing leaves moisture that causes steaming not searing; a pan that is not hot enough gives pale, soft tofu; moving tofu too soon stops the crust forming — let it sear undisturbed first.