1/2 teaspoon garlic chili sauce (or more to taste)
Wrap tofu in a few layers of paper towel or a clean, dry dishcloth. Place wrapped tofu under a heavy pot or under a plate weighted with some canned goods. Allow to sit for 10 minutes.
Cut tofu into approximately 1" cubes.
To a large shallow dish, add ingredients for marinade and whisk to combine. Add cubed tofu and toss until all sides are coated. Marinate for at least 15 minutes, stirring halfway through. Transfer tofu, piece by piece to a large freezer bag. Reserve marinade and whisk in 1 Tbsp corn starch.
Add remaining 2 Tbsp of cornstarch to freezer bag, seal bag and toss to combine. Tofu should have a gummy coating.
In a large non-stick sauté pan or wok over medium-high heat, heat 2 Tbsp of the canola oil. Carefully add tofu and stir-fry for about 4 minutes, stirring and flipping tofu pieces to evenly brown on all sides. Remove tofu and set aside.
Add remaining canola oil and heat over medium-high. Add green onions, stir-fry for one minute. Add garlic and ginger and stir-fry for another 30 seconds.
Add reserved marinade, reduce heat to medium and simmer until sauce thickens, about 2 minutes. Add tofu pieces and stir to combine and evenly coat tofu. Sprinkle with sesame seeds.
Serve immediately to enjoy the crispy tofu bits.