Make the cornstarch slurry by whisking together the cornstarch and 2 tbsp (30 mL) water in a small bowl. Set aside.
Add the rest of the ingredients, including the remaining 1/4 cup (60 mL) water, to a large skillet over medium heat. Whisk and bring to a boil, whisking often.
Whisk in the cornstarch slurry. Bring heat to medium low and cook, whisking for about a minute - until the sauce thickens.
Stir in the crispy tofu and serve topped with green onions and sesame seeds.