For stock: Pour stock into a small pot and bring to a boil. Stir in salt and continue to boil until the stock has reduced by half. Remove from heat. Sprinkle gelatin into a bowl of ½ cup water and allow gelatin to bloom (you will know the gelatin is ready, when it expands and absorbs all the water).
Pour the gelatin mixture into the hot stock, stir until dissolved and pour into a shallow, 8”x11” baking dish. Cover and refrigerate for at least 6 hours, but preferably overnight until an aspic forms (the stock gelatinizes). Once aspic is ready, cut into ½ inch squares and continue to refrigerate until ready to use.
For filling; In a large mixing bowl, combine all the ingredients and gently mix together until fully combined, making sure not to overwork the meat mixture. Cover and refrigerate for at least an hour or until ready to use.
To assemble: Brush some egg wash over the surface of a wonton wrapper and fill with 2 teaspoons of filling. Top filling with 1 or 2 small cubes of aspic and carefully gather the perimeter of the wonton and pull it until the center, to create a pouch. Gently twist the gathered wonton to seal the pouch and pinch off the end.
Line a bamboo steamer (or whatever steaming device you have) and line it with a single layer of savoy or napa cabbage. Place steamer over a pot filled up halfway with water (like a double boiler) and boil over medium-high heat. Steam dumplings for about 10 to 12 minutes or until the filling has cooked through and the stock has melted into a liquid.
Allow dumplings to cool for 1 to 2 minutes before serving in the steamer.