Place the duck meat, stock. Mirepoix and sachet in a pot.
Bring to a simmer over low heat and cook slowly until the meat is extremely tender, about 2 to 2 ½ hours.
Strain out the duck meat and transfer to a mixing bowl. Let the meat cook slightly.
Mix the duck meat with the paddle attachment until the meat breaks into pieces. Add enough of the reserved stocked and fat from the stock produce a spreadable consistency.
Pack this mixture into crocks or timbales. Pour enough melted duck over the duck to coat and seal. Cover and refrigerate until ready to server or to use in other preparations.