Heat the oven to 180 °C.
Remove the skin and bones from the cooked chicken. Tear the meat into thumb-sized strips and set aside.
Heat the oil in a large pot and add the onion. Fry over a medium heat for 5 minutes, or until the onions are soft
Add the wine and herbs and simmer for 5 minutes, or until the liquid in the pan has reduced by half. Add the 500ml water.
In a separate small bowl, mix the two KNORR soup powders with 125ml water to form a smooth paste. Add this to the pan and simmer gently, stirring occasionally, for 5 minutes, or until thick.
Add the mixed vegetables (no need to thaw them first) and simmer over a low heat for another 7 minutes, or until the veggies are just cooked through.
Remove the pan from the heat and stir in the chicken strips and cream. Add extra cream if sauce is too think. Set aside.
To make the crust, unroll the thawed pastry and place on a sheet of clingfilm. Place an ovenproof pie dish upside down on the pastry and, with a sharp knife, cut all the way round, following the rim of the dish but allowing an extra 2 cm on all sides.
Use the left-over pastry to cut out a few leaf shapes for decorating the pie.
Stir the lemon juice into the cooled pie filling and season to taste with salt and pepper.
Grease the pie dish and fill to the top with the chicken mixture.
Place the pastry lid on top, lightly press the edges to the rim of the dish to seal, and decorate with pastry leaves. Brush the lid and leaves with the beaten egg, then cut a small slit in the centre of the pie crust.
Bake at 180 °C for 30 minutes, or until the crust is puffed and golden and the filling is piping hot.
Serve with a crisp green salad or creamed spinach.