Spray two 12-hole mini muffin pans (1 1/2 tblsps capacity) with cooking oil. Line pan holes with 24 wonton wrappers. Freeze remaining wrappers.
Place chicken, chestnuts, onions, breadcrumbs, peanut butter, sauce and kecap manis in a large bowl. Mix well. Roll heaped tblsps of chicken mixture into 24 balls.
Gently push a ball into centre of each wonton wrapper. Sprinkle with nuts. Gather edges of wrappers in towards centre of filling. Lightly spray with cooking oil.
Cook in a moderate oven (180C) for 25 minutes, or until filling is cooked through and wonton wrappers are golden. Remove from oven. Stand for 5 minutes in pans.