1. Bring large stockpot of salted water to a boil. Prepare an ice-water bath; set aside. Trim and discard stems of broccoli rabe. Place broccoli rabe in boiling water; cook until tender and bright green, about 2 minutes. Drain, and transfer to ice bath to stop cooking. Drain again. Finely chop, and set aside.

2. Heat oil in medium skillet over low heat. Add garlic; cook 1 to 2 minutes. Raise heat to medium. Add broccoli rabe and pine nuts. Season with salt and pepper; cook 5 minutes. Transfer to food processor. Pulse until finely chopped, but not pureed, about 15 pulses.

3. Lightly dust parchment-lined baking pan with cornstarch, and set aside. Place a dumpling skin on a clean surface. Using your fingertip, wet edge of both sides of skin. Place 2 teaspoons broccoli rabe mixture in center. Draw up edges; make a small pleat. Squeeze pleat firmly together; continue making pleats until dumpling is sealed. Place completed dumpling on prepared pan. Loosely cover with plastic wrap. Repeat process, using remaining skins and filling.

4. Fill wok or a high-sided saucepan with water; bring to a boil. Reduce heat to medium, bringing water to a simmer. Using a pastry brush, generously brush top and bottom compartments of large bamboo steamer basket with oil. Brush any excess cornstarch from dumplings; arrange loosely in compartments. Assemble steamer, cover, and place over simmering water. Steam until wrappers are soft and filling is heated through, 10 to 12 minutes, switching top and bottom compartments halfway through steaming.

5. Pour 1 teaspoon parsley oil into a Chinese soup spoon; place dumpling on top. If using another vessel, drizzle oil over dumpling. Garnish with a parsley leaf, and serve.