Heat oven to Gas Mark 6.

Heat half the butter in a frying pan and cook the mushrooms and gammon for 5 minutes, put to one side for later.

In the same pan melt remaining butter, add flour and cook for 1 minute.

Add stock, whisk until smooth, add cream.

Add chicken, mushrooms and gammon to sauce, mix and pour in to shallow pie dish(es).

Roll out pre-prepared pastry, use to top pie dish(es), bush with beaten egg and cook for 25 minutes.