1. Cut half block of tofu in half horizontally, making two thin layers. To remove excess water, place three layers of paper towel on a dinner plate, then lay two layers of tofu on top. Cover tofu with three more layers of toweling, then top with another dinner plate as a weight. Let tofu sit for 15 minutes while you prepare rest of recipe.
2. If using square wonton wrappers, cut them into rounds. Use a 2- to 3-inch round cookie cutter, or trace around the bottom of a glass with a sharp paring knife. Discard trimming and cover rounds with a damp paper towel; set aside.
3. Prepare shumai filling. Slice white and green parts of scallions, keeping the two parts separate. Reserve scallion greens to use in dipping sauce. Combine scallion whites in a medium bowl with cabbage, ginger, egg white, soy sauce, sesame oil, salt, and sherry if using; stir well and set aside.
4. In a small, microwavable bowl, combine all dipping sauce ingredients, adding reserved sliced scallion greens. Microwave mixture on high for 1 minute; alternately, bring to a simmer in a small saucepan. Let sauce cool. Prepare steamer of your choice; let water heat while assembling shumai.
5. Remove tofu from paper towels and add to bowl with other shumai filling ingredients. Using a potato masher or a fork, mash tofu until it resembles coarse crumbs, then stir all filling ingredients together until well combined. Place a single wonton wrapper on a piece of waxed paper, then drop 1 rounded teaspoon of shumai filling in center. Dip your finger in water and use it to slightly moisten edge of wrapper. Bring up edges of wrapper, pinching it gently around filling, and leaving filling exposed at top. Garnish by gently pressing 1 edamame bean into top of shumai, if desired. Set completed shumai aside on a clean piece of waxed paper or plate while you assemble remaining shumai. There should be enough filling for 24 wrappers.
6. When steamer is ready, spray it lightly with cooking spray. Transfer assembled shumai to steamer, placing them so they aren't touching each other. Cover and steam for 12 minutes over simmering (not boiling) water. When done, edamame beans will be lighter green in color. Remove shumai from steamer. Serve immediately with dipping sauce.
Source: Hannaford fresh Magazine, May - June 2008