Drain the 400 g block of extra-firm tofu. Wrap in a clean kitchen towel or paper towels and place under a weighted board or pan for 15–30 minutes to remove excess moisture. After pressing, cut the tofu into 2 cm (about 3/4 inch) cubes or rectangular bite-sized pieces.

Marinate

In a bowl, whisk together 3 tbs light soy sauce, 1 tsp dark soy sauce, 1 tbs mirin, 1 tsp sesame oil, 1 tsp kosher salt, and 1 tsp black pepper. Add the pressed tofu pieces and gently toss so each piece is coated. Let marinate 10–15 minutes at room temperature (do not exceed 30 minutes as tofu can become too soft).

Coat with cornstarch

After marinating, drain excess marinade (reserve a tablespoon of marinade to add to the sauce if desired). Sprinkle 3 tbs cornstarch over the tofu and gently toss until each piece has a thin, even film of cornstarch. This will create a crisp crust when fried.

Frying

Heat oil

Pour about 250 ml neutral oil into a heavy skillet or a deep pan to a depth of roughly 1.5–2 cm (enough for shallow frying). Heat over medium-high until oil registers 175–180°C (350–360°F) or until a small piece of tofu sizzles immediately on contact.

Fry tofu in batches

Carefully add tofu pieces in a single layer without crowding—work in 2–3 batches depending on pan size. Fry each batch 3–4 minutes per side, turning occasionally, until all sides are golden-brown and crisp. Use a slotted spoon or spatula to transfer fried tofu to a wire rack or paper towels to drain. Keep warm in a low oven (100°C / 210°F) if necessary while finishing remaining batches.

Sauce

Prepare sauce base

Wipe out most of the frying oil from the skillet, leaving about 1–2 tbs of oil and any fond for flavor. Return skillet to medium heat and add 2 tbs neutral oil and 1 tbs unsalted butter. Once butter melts and foams, add 4 cloves minced garlic and 1 tsp grated fresh ginger. Sauté 30–45 seconds until fragrant but not browned.

Combine liquids and simmer

Add 3 tbs light soy sauce, 1 tsp dark soy sauce, 1 tbs rice vinegar, 1 tbs brown sugar, and 60 ml water to the skillet. If you reserved a tablespoon of tofu marinade, add it here. Stir to dissolve sugar and bring the sauce to a gentle simmer.

Thicken sauce

Stir the cornstarch slurry (1 tbs cornstarch mixed with 1 tbs water) to recombine, then pour it into the simmering sauce while stirring continuously. Cook 1–2 minutes until sauce thickens to a glossy, pourable consistency. If sauce becomes too thick, add 1–2 tbs water to loosen.

Finish the sauce

Remove the skillet from heat and stir in 1 tsp toasted sesame seeds, 2 thinly sliced green onion stalks, and 1/4 tsp red pepper flakes if using. Adjust seasoning to taste—add a dash more soy for saltiness or a little more sugar for sweetness.

Toss tofu in sauce

Return the fried tofu to the skillet (or a large mixing bowl) and gently toss to coat every piece evenly with the soy-garlic glaze. Work quickly so the tofu retains some crispness but is well coated. If using a skillet, return to low heat for 30 seconds to warm through while tossing.

To Serve

Transfer sauced tofu to a serving plate over steamed rice or noodles if desired. Garnish with extra thinly sliced green onions and a sprinkle of extra toasted sesame seeds. Serve immediately so the tofu remains crisp on the outside and tender inside.