Mushroom Stuffed Chicken 'En Croute'

olive oil
½ red onion, finely chopped
2 rindless bacon rashers, finely
diced
12 button mushrooms, finely diced
freshly ground salt & pepper
4 boneless, skinless chicken breasts
¼ cup milk
1 egg
4 sheets of puff pastry
olive oil spray
Preheat oven to 180°-190°C. Heat 1 tbsp oil in a non-stick pan and gently saute onion, bacon and mushrooms until soft, together with seasonings. Slit open the thickest part of the chicken breasts to make a cavity. Then stuff with onion mixture. Whisk milk and egg, paint the cut edge of chicken breasts and press down firmly. Season and place on a pastry sheet. Brush the edges with egg wash and fold up like an envelope. Then lightly brush all over with more egg wash and place on a lightly oiled oven tray, seam side down. Mark a criss-cross pattern lightly on each parcel and cook in oven for about 30-35 mins until chicken is cooked and pastry is golden.