Press the tofu: Wrap the tofu block in a clean towel and place a heavy skillet or books on top for 15–20 minutes. This removes excess moisture so it crisps better.
Make the sauce: In a small bowl, whisk soy sauce, water, rice vinegar, maple syrup or honey, sesame oil, garlic, ginger, cornstarch, and red pepper flakes if using.
Set aside. Stir again just before using.
Prep the veggies: Cut broccoli into bite-size florets, slice pepper and carrot, and trim snap peas. Keep them similar in size so they cook evenly.
Cube and coat the tofu: Cut pressed tofu into 3/4-inch cubes.
Toss with 1 tablespoon cornstarch and a pinch of salt until lightly coated.
Crisp the tofu: Heat a large nonstick skillet over medium-high heat. Add the neutral oil, then tofu in a single layer. Cook 8–10 minutes, turning occasionally, until golden on most sides.
Remove to a plate.
Stir-fry the veggies: In the same pan, add a splash of water if dry. Add broccoli and carrots first and cook 3 minutes. Add bell pepper, snap peas, and the white parts of the green onions.
Stir-fry 2–3 more minutes until tender-crisp.
Combine with sauce: Lower the heat to medium. Return tofu to the pan. Give the sauce a final whisk and pour it in.
Stir gently for 1–2 minutes until glossy and thickened, coating the tofu and veggies.
Finish and garnish: Remove from heat. Sprinkle with sesame seeds and the green onion tops.
Portion for meal prep: Divide among 3–4 containers. If using a base like cauliflower rice or brown rice, portion that first, then add the tofu and veggies on top.