1.Cover mushrooms with boiling water in a heatproof jug. Stand for 30 minutes. Drain; reserve liquid. Finely chop mushrooms; transfer to a medium bowl to use in wontons.
2.Preheat grill on high. Grill onion and garlic, cut-side-up, ginger and 2 of the chillies in an ovenproof dish for 15 minutes or until aromatic and charred.
3.Place charred ingredients in a large stock pot with reserved carcass, star anise, cinnamon and coriander roots and stems, stock and reserved mushroom liquid. Bring to the boil. Reduce heat to low; simmer; covered, for 1½ hours.
4.Meanwhile, make wontons. Combine duck meat and mushrooms in a bowl with water chestnuts, green onion, garlic, ginger, sauce and oil; season. Place 3 teaspoons filling in the centre of each wrapper; wet edges with water, then bring together and pinch to seal.
5.Strain broth through a fine sieve, discarding solids. Transfer to a large saucepan; add sauces, season. Bring to a simmer; cook wontons in soup for 2 minutes or until wrappers have softened and filling is hot.
6.Divide vegetables and wontons between 4 large serving bowls. Divide hot broth between bowls.
7.Seed and thinly slice remaining chillies lengthways. Serve the broth topped with chilli, onion, reserved coriander leaves and crispy duck skin.
To crisp duck skin, place on a rack over an oven tray. Bake at 160°C for 15 minutes or until crisp and fat has rendered from skin.
This recipe is not suitable to freeze.Note