In a skillet over high heat, whisk together all the sauce ingredients.
Bring to a boil, then reduce the heat to medium. Let it cook until thick, for a couple minutes. Stir it continuously.
In a second skillet, add in the 3 tbsp avocado oil over medium heat.
While the skillet is heating, toss the cornstarch with the cubed tofu in a bowl.
Once the skillet is hot, evenly spread the tofu cubes on it.
Let them cook over medium heat for about 4 minutes per side, then flip the pieces and repeat on the other side. Move the tofu around as it cooks, so it doesn't stick to the bottom of the skillet.
Once crispy, pour the sauce over top. Cook for another minute or so, until the sauce has thickened over the tofu.
Remove from the heat and sprinkle the tofu with black sesame seeds. Serve hot with rice!