Step 1: Press the extra-firm tofu. Wrap the block of tofu in several layers of paper towels or a clean kitchen towel. Place it on a plate, then place a heavy object (like a few cookbooks or a cast iron pan) on top. Let it press for at least 20-30 minutes to remove excess water.
Step 2: Once pressed, unwrap the tofu and cut it into 1-inch cubes. In a medium bowl, toss the tofu cubes with 1 tablespoon of cornstarch, a pinch of salt, and a dash of black pepper until evenly coated.
Step 3: Chop all your chosen vegetables into bite-sized pieces. Remember to aim for uniform sizes for even cooking.
Step 4: In a small bowl, whisk together the stir fry sauce ingredients: low-sodium soy sauce, rice vinegar, sesame oil, maple syrup, grated fresh ginger, minced garlic, and a pinch of red pepper flakes (if using). In a separate tiny bowl, mix the remaining 1 tablespoon of cornstarch with 2 tablespoons of cold water to create a slurry. Set both aside.
Step 5: Heat 1 tablespoon of cooking oil in a large wok or a large non-stick skillet over medium-high heat. Once hot, add the coated tofu in a single layer. Cook for 5-7 minutes, turning occasionally, until all sides are golden brown and crispy. Remove the cooked tofu from the pan and set it aside.
Step 6: Add the remaining 1 tablespoon of cooking oil to the same wok or skillet. Add the harder vegetables first (e.g., broccoli, carrots) and stir fry for 3-4 minutes until they start to soften but are still crisp-tender.
Step 7: Add the quicker-cooking vegetables (e.g., bell peppers, snap peas) and stir fry for another 2-3 minutes until they are bright and tender-crisp.
Step 8: Pour the prepared stir fry sauce over the vegetables in the pan. Bring it to a gentle simmer. Give the cornstarch slurry a quick re-whisk, then slowly pour it into the simmering sauce while stirring constantly. The sauce will thicken almost immediately.
Step 9: Return the crispy tofu to the pan, gently tossing everything together to ensure the tofu and vegetables are well coated with the delicious sauce. Cook for just 1-2 more minutes to heat the tofu through and allow the flavors to meld.
Step 10: Remove from heat. Serve immediately over your choice of grain, garnished with sesame seeds and fresh green onions if desired.