Step 1In a small bowl, combine the soy sauce, vinegar and sugar, stirring until the sugar is completely dissolved. Add the green onion, garlic, chile and black pepper, and stir to combine. Set aside. This makes about one-third cup dipping sauce.
Step 2Pan-fry the cubes of tofu in a wok or medium, heavy-bottom saucepan: Add enough oil to coat the bottom of the wok or pan and heat over medium-high heat until hot. Test the oil with one cube of tofu, adjusting the heat as necessary so the cube fries quickly but does not burn. Fry the cubes in a single layer, making sure the pieces do not touch, until crisp on all sides, 5 to 7 minutes total. Repeat until all of the tofu pieces are cooked; this may need to be done in 2 batches.
Step 3Drain the pieces on a paper towel-lined plate.
Step 4Serve the fried tofu hot with the dipping sauce on the side.