Open the package of tofu and drain out the water. Next, wrap the tofu block in a paper towel (or tea towel) and place it on a plate or tray. Now, press the tofu: First, put another tray or plate or even a cutting board on top of the tofu block to evenly distribute the weight. Then, place a heavy item* (I used a marble mortar but a can of food works) on top to apply pressure. Let it sit for at least 30 minutes before using. *The weighted item should not be so heavy that it will crumble or crush the tofu block but heavy enough that it will press out the tofu's liquid.
To make the homemade teriyaki sauce, whisk the sauce ingredients in a (microwave-safe) medium bowl. If the sugar doesn't dissolve easily, microwave it for 30 seconds and whisk well. Set aside.
Cut the green onion diagonally into thin slices.
After 30 minutes of draining the tofu, remove the paper towel and transfer the tofu to the cutting board. First, cut the tofu block in half widthwise.
Next, cut the tofu into roughly ¾-inch (2 cm) cubes.
Put the potato starch in a shallow tray or bowl and gently coat the tofu cubes with the potato starch. Set aside.
To Pan-Fry the Tofu
Heat a large frying pan on medium-high heat. When it's hot, add half of the oil (keep the other half for the next batch) and distribute it evenly. Add the first batch of tofu cubes to the pan, placing them about 1 inch (2.5 cm) apart from each other so it's easy to rotate the tofu cubes without sticking to each other.
Fry the cubes on one side until golden brown, then turn them to fry the next side. Repeat until all sides are brown and crispy. Transfer the fried tofu cubes to a plate or tray lined with a paper towel.
Add the next batch of uncooked tofu to the pan and fry until crispy and golden brown on all sides. Add the remaining oil if necessary, which helps brown the tofu faster.
Remove all the fried tofu to the plate/tray.
Wipe off any remaining oil in the pan with a paper towel. Then, transfer the tofu back into the pan.
Add the teriyaki sauce to the pan; the sauce will start to thicken immediately. Quickly toss the tofu cubes in the sauce to coat, then turn off the heat and remove the pan from the stove. Tip: The sauce will continue to thicken with the residual heat, so if you want to keep some sauce in the pan, be sure to turn off the heat as soon as the tofu is coated.
Serve the tofu and blanched broccoli over the steamed rice. Garnish the tofu with green onions and sesame seeds.
You can keep the leftovers in an airtight container and store in the refrigerator for 3 days. Since the texture of the tofu changes when frozen, I don't recommend storing the tofu in the freezer.