Preheat the oven to 95°C. Cut the tofu in half horizontally and lay between layers of paper towels. Place on a plate, top with another plate, and place a weight on top (a 14-ounce can of vegetables works well). Let stand 20 minutes. After 20 minutes, cut the tofu into 1/4-inch cubes and place in a large mixing bowl. Add the carrots, cabbage, red pepper, spring onions, ginger, coriander, soy sauce, hoisin, sesame oil, egg, salt, and pepper. Lightly stir to combine.
To form the dumplings, remove 1 wonton wrapper from the package, covering the others with a damp cloth. Brush the edges of the wrapper lightly with water. Place 1/2 rounded teaspoon of the tofu mixture in the center of the wrapper. Shape as desired. Set on a sheet pan and cover with a damp cloth. Repeat procedure until all of the filling is gone.
Using a steaming apparatus of your choice, bring 1/4 to 1/2-inch of water to a simmer over medium heat. Spray the steamer's surface lightly with the non-stick vegetable spray to prevent sticking. Place as many dumplings as will fit into a steamer, without touching each other. Cover and steam for 10 to 12 minutes over medium heat. Remove the dumplings from the steamer to a heatproof platter and place in oven to keep warm. Repeat until all dumplings are cooked.