1Heat a medium frying pan over high heat until hot. Add the oil and mushroomsand cook, stirring occasionally, for 5 minutes or until mushrooms are tender and the pan juices evaporated. Set aside to cool 15 minutes.
2Combine the pork mince, ginger and water chestnuts in a food processor. Drain any excess juices from mushrooms and add to the processor. Process until well combined, transfer to a bowl and store in the oyster sauce and kecup manis, mix well.
3Place one wonton wrapper on a clean surface. Spoon a heaped teaspoonful of mushroom and pork mixture onto the centre of the wrapper. Use a pastry brush dipped in water to brush the edges. Fold the wrapper diagonally to enclose the filling. Brush one corner with water and bring down under the filling to meet the second corner and press to join together. Place on a plate. Continue with remaining mushroom mixture and wonton wrappers.
4Half fill a large frying pan or wok with hot water & bring to the boil over high heat. Line a bamboo steamer with baking paper and arrange the wontons, 2cm apart, in the steamer. Place the steamer over the simmering water, cover with the steamer lid and cook, in batches, for 4 minutes or until cooked through.
5Serve the hot wontons with sweet chilli sauce for dipping.
Note: Wonton wrappers are available, fresh & frozen, from Asian food stores & some supermarkets.