Heat 2 tbsp (30 mL) canola oil in skillet over medium-high heat. Cook mushrooms until slightly softened, about 2 min. Add half the green onions and the garlic. Cook, stirring, 1 min. until fragrant. Transfer to large bowl to cool completely. Mix in pork, soy sauce, sesame oil and cornstarch.
Lay 1 wrapper on work surface and brush edges with water. Place 1 1/2 tsp (7 mL) filling in centre. To make "flower" dumplings, bring the 4 corners of the wrapper together in the centre over the filling. Pinch to seal the 4 "openings", creating an "X" pattern on top of the dumpling. Pinch the centre to close any holes. (Or to make dumpling "purses", draw up 2 opposite corners of each wrapper, press edges together, then press 3 or 4 pleats along sealed edge.) Place dumplings on parchment paper-lined baking tray. Make 48 dumplings.
You can either pan-fry or steam dumplings. To pan-fry in batches of 12: Heat about 1 tbsp (15 mL) oil in large non-stick skillet set over medium-high heat. Place batches of dumplings (flat-side down, if flower-shaped) in skillet and cook about 1 min. or until bottoms start to brown. Add 2/3 cup (150 mL) water; cover and cook 8 to 10 min. until filling is cooked through, bottoms are crispy and wrappers are tender. To steam: Working in batches, arrange dumplings in single layer in parchment-lined steamer. Fit steamer over wok or saucepan with 2 in. (5 cm) simmering water in bottom (do not let water touch dumplings). Cover and steam 6 to 8 min. until filling is cooked through and wrappers are tender.
Arrange dumplings on serving platter. Garnish with remaining green onions. Serve with hoisin sauce
To freeze, lay dumplings in a single layer on a parchment-lined baking sheet. Freeze for 2 hr. until hard, then transfer to a re-sealable plastic bag. Dumplings can be frozen up to 1 month. To cook from frozen, pan-fry or steam about 15 min.