Preheat the oven to 200 degrees F (95 degrees C).
Cut the tofu horizontally in half and put the slices on a plate between paper towels. Put another plate on top and a can of vegetables (or similar) to act as a weight. Let the tofu stand for 20 minutes.
Cut it into ¼ inch cubes and put them in a mixing bowl. Add the cabbage, carrots, green onions, red bell pepper, cilantro, ginger, soy sauce, sesame oil, hoisin sauce, salt, pepper and egg and stir gently.
Brush the edges of a wonton wrapper with water and add ½ teaspoon of the tofu mixture to it. Shape the wonton as desired, perhaps into a triangle, ensuring there is no air trapped inside. Repeat with the remaining wonton wrappers and filling, keeping the prepared wontons covered in a damp cloth.
Bring ½ inch of water to a simmer over a moderate heat and spray the inside of your bamboo steamer with nonstick cooking spray. Arrange as many tofu dumplings in your steamer as will fit without touching, then cover the steamer with its lid and steam for 10 minutes over a moderate heat. Transfer the done ones to a heatproof platter and keep in a warm oven until all the dumplings are done.