Drain the tofu. Wrap it in paper towels, then in an absorbent tea towel and place it under something heavy to press.
Meanwhile, combine the soy sauce, pineapple juice, brown sugar, ginger, garlic and 1 tablespoon plus 1 teaspoon of cornstarch in a bowl.
After the tofu has press for at least 15 minutes, cut it into small cubes about ½ inch (1.25 cm).
Place the tofu in a container and add 2 tablespoons of cornstarch. Place the lid on the container and shake well to coat the tofu in cornstarch. If it’s not coated enough, add an additional tablespoon of cornstarch.
Heat the oil in a large pan over medium high heat. Fry the tofu, flipping occasionally, until the tofu is golden on all sides.
Lower the heat to low and add the chopped pineapple. Stir the teriyaki sauce to dissolve the cornstarch and pour it into the pan. The sauce should thicken quickly. Toss the tofu to coat it in the sauce.
Serve over rice and garnished with green onion, if desired.