In a cast-iron pan over medium-high heat, add the oil. Toss the tofu with the cornstarch, brown sugar, salt and pepper. Place the cubes into the oil, making sure they don't stick to the bottom of the pan by moving them around a bit. Cook and turn when brown, about 1 minute per side. Continue to cook and turn the tofu until all sides are browned. Remove to a paper-towel-lined plate and add more ground black pepper to taste until well coated.
In the meantime, in a small bowl, whisk together the agave, ponzu, basil, ginger and scallions.
To serve, place the tofu bites on a platter with the dipping sauce on the side in a bowl.