Sauté onions in butter in large pan until just tender. Add pork and seal on all sides. Stir in flour and cook for 1-2 minutes.
Gradually stir in cider or stock. Bring to boil and simmer for 20 minutes. Stir in sage, mustard and cream, season with salt and pepper and then allow filling to cool.
Divide filling between 12 individual pie dishes of your choice. Roll out pastry and cut out 12 tops - each slightly larger than the dish, cut strips from remaining pastry and use to cover rims of dishes - which you have brushed with beaten egg, then glaze with beaten egg.
Top dishes with the pastry lids, press down edges and trim excess pastry, knock up edges. Cut slits in top to allow steam to escape. Brush with beaten egg and sprinkle with poppy seeds to decorate.
Bake for 20 - 25 minutes or until pastry is golden brown.