Filling: Heat the butter in a frying pan, add the bacon and mushrooms and cook, stirring, until the liquid has evaporated. Add the green onions and cook, stirring, until soft. Stir in the mustard, cream cheese, cream and chicken and mix well. Layer 5 sheets of filo pastry together, brushing each layer with melted butter. Keep the unused pastry covered with a barely damp, clean dish towel at all times to prevent drying out. Cut the pastry in half to form two squares. Spoon one fourth of the filling onto the end of each square, roll once, tuck the ends in and roll up. Brush lightly with butter and then sprinkle with poppy seeds. Repeat with the remaining pastry and filling. Place on a lightly greased baking sheet. Bake at 400 degrees for about 20 minutes or until lightly browned and filling is hot. The parcels can be prepared a day ahead. Store, covered with plastic wrap, in refrigerator.