Hearty chestnut pork zongzi with rich meat and sweet chestnut filling are a protein-packed festival treat. A family Dragon Boat tradition.
Rinse the glutinous rice until the water runs clear and soak in water for at least 3 hours. Soak dried shiitake mushrooms in warm water until soft, then squeeze out the water and trim stems.
Cut pork belly into 2-inch chunks. Marinate pork and mushrooms together with soy sauce, oyster sauce, Shaoxing wine, five spice powder, white pepper, sugar, and salt for at least 1 hour in the refrigerator.
Wash bamboo leaves thoroughly and soak in hot water for 30 minutes to make them pliable. Drain and wipe dry with a clean towel.
Drain soaked rice. Season the rice with a spoonful of soy sauce and sesame oil for color and flavor.
To assemble: Lay 2 bamboo leaves overlapping, forming a cone. Fill with 2 tbsp of rice, then layer on chestnut, pork, mushroom, and egg yolk. Top with more rice to cover. Fold and tightly wrap into a triangle or pyramid and secure with kitchen twine.
Repeat assembly until all fillings and rice are used.
Place wrapped zongzi in a large pot, fill with water covering all zongzi completely, and weigh down with a heat-proof plate if needed. Bring water to a boil, then reduce to a gentle simmer and cook for 3 hours, checking the water level periodically.
Remove zongzi with tongs and allow to cool slightly before unwrapping. Serve warm.