Prepare and Dry Tofu: Drain the tofu block and gently pat it dry using paper towels. Change the towels a few times to soak up as much moisture as possible. Press the tofu lightly to remove extra water without causing it to crumble. Slice the block horizontally into two slabs, then cut into roughly 1-inch cubes. Arrange the cubes on a large plate or a rimmed baking sheet, and gently pat them dry again to ensure minimal moisture for better crisping.
Coat Tofu with Cornstarch: Gradually sprinkle 2 tablespoons of cornstarch over the tofu cubes. To get an even coating, add the cornstarch in small increments (about half a tablespoon at a time), tossing gently after each addition with your fingers until the cubes are lightly but thoroughly dusted.
Mix the Sauce: In a small bowl or liquid measuring cup, whisk together soy sauce, water, hoisin sauce, rice vinegar, minced garlic, minced ginger, and the remaining 1 teaspoon of cornstarch. Set this flavorful mixture aside.
Cook Broccoli: Heat 1 tablespoon of the neutral oil in a large nonstick skillet or wok over medium-high heat. Once the oil shimmers, add the broccoli florets along with salt and pepper. Stir occasionally and cook until the broccoli becomes bright green and crisp-tender, about 5 minutes. Transfer the broccoli to a plate and set aside.
Sear the Tofu: Add the remaining 2 tablespoons of oil to the skillet and increase the heat to medium-high. Arrange the tofu cubes in a single layer and cook, turning gently every 3 minutes or so, until golden and crisp on all sides. The tofu may stick together or crumble slightly; use a sturdy spoon to separate pieces carefully. Don’t worry about any crumbles—they add extra texture and flavor.
Combine and Finish: Return the cooked broccoli to the skillet with the tofu. Pour the prepared sauce evenly over the mixture and stir to coat everything well. Let it cook for about 1 minute until the sauce thickens and the broccoli is heated through. Remove from heat, stir in the toasted sesame oil and chopped green onions, then sprinkle with toasted sesame seeds.
Serve: Serve your broccoli tofu stir fry hot, alongside cooked brown rice or quinoa for a balanced meal.