Preheat oven on to 180°C. Roll out the pastry on a floured surface and trim to make a rectangle about 24 x 36 cm.
Cut the pastry in half, lengthways and cut each half into 3 equal squares, about 12 cm along each side, using a small knife or scissors.
Push each square into the oiled tin, making sure it is pushed right into the edges
Use scissors , or a small knife to cut the chicken into strips and cut into chunks. Put chunks in a bowl. Add corn, peas, cream and mustard. Mix together. Season well.
Divide mixture between the pies. Fold the tops of the pies over roughly and press together.
Brush the pastry with the beaten egg. Bake in the oven for 35 minutes or until they brown and the filling bubbles
