Cut the tofu into large cubes (about 1-inch), about 32 cubes per box. Lay the cubes on a paper towel and let them dry a bit.
Toss them in the cornstarch, shaking off excess.
Heat a large fry pan. Add the oil. Heat until the oil is shimmering. Add about half the tofu to the pan. Let it cooked undisturbed until the first side is golden brown, flip, brown a second side, repeat until most sides are brown.
Remove from pan to a plate and repeat with the second batch, remove.
Add garlic and ginger to the pan and cook until fragrant, less than one minute. S
prinkle brown sugar into the pan, toss quickly for 30 seconds or so.
Add the tamari and mirin, allow to bubble and reduce for a minute.
Add back the tofu cubes back to the pan and carefully toss with liquid in the pan.
Shut the heat off and continue tossing until well coated.
Sprinkle with green onion, chilies and pepper.Serve immediately for best results.