For each packet: roll out the pastry and cut a square large enough to be folded around the breast. Place one chicken breast in the middle, sprinkle with salt, pepper and sage. Place a knob of butter and some mushrooms on it and fold the breast over. Squeeze some lemon juice and pour a little white wine over it. Then seal, bringing the corners up to the center. Brush with beaten egg. Repeat for each packet.

Place them on an ungreased cookie sheet (I usually put foil on the cookie sheet - it saves clean-up) and put in the oven for about 1/2 an hour or until the pastry is nice and brown. The cooking time will vary, according to the size of your packets, but the butter should keep the chicken nice and moist.

Serve with a couple of vegetables (asparagus is really nice with this), but I don't usually bother with potatoes - the pastry fills that role.