Wipe tofu dry with paper towels. Cut the tofu in each box in half, then cut each half into four equal portions. Flour each portion lightly. Heat vegetable oil to medium hot (350 to 375 degrees). Add the tofu, a few at a time. Fry until golden and remove to drain on paper towels. Prepare sauce by placing the water, soy or tamari sauce, sweetener and stock in a saucepan. Bring to a boil and mix well, making sure sugar (if using) is dissolved. To serve, place a small amount of the sauce on four warmed plates. Divide the tofu evenly among the plates, placing them on the sauce. Garnish with grated ginger and chopped scallions.