Heat the butter and oil in a large frying pan then fry the game, in batches, until browned. Lift out and put into a large casserole dish. Add the onion and bacon to the frying pan and fry for 5 minutes, stirring until golden. Mix in the flour then stir in the wine, stock and redcurrant jelly. Add the berries, bouquet garni and seasoning, then bring to the boil. Tip the sauce over the game, cover and cook in a preheated oven, 160°C (325°F), Gas Mark 3, for 1¼ hours. Allow to cool.
Lift out the game and take the meat off the bone. Return to the sauce, discard the bouquet garni then spoon into a 1.2 litre (2 pint) pie dish.
Roll the pastry on a lightly floured surface until a little larger than the top of the pie dish. Cut 1 cm (½ inch) wide strips from the edges and stick on to the dish rim with beaten egg. Brush the pastry strips with egg and lay the sheet of pastry on top. Press down, trim off the excess then flute the edges. Cut leaves from reformed trimmings. Chill, uncovered, until required.
When ready to serve, brush the pie with beaten egg then cook in a preheated oven, 200°C (400°F), Gas Mark 6, for 25–30 minutes until golden and piping hot inside. Serve with steamed Brussels sprouts and braised red cabbage, if liked.