Cut all the game meats into 1cm (½ in) pieces and put in a large bowl with the bacon, rum, wine, mushrooms and tarragon. Cover and leave to marinate in a cool place for at least 3 hours or overnight.
Put the stock in a saucepan with the onion and allspice. Bring to the boil, cover and simmer for 30 minutes. Drain the meats thoroughly and add the marinade liquid to the pan. Boil rapidly over a hight heat until reduced to about 200ml (7fl oz). Strain and set aside, reserving the stock.
Heat the oven to 160°C (325°F, gas mark 3). For the pastry, sift the flour, sugar and salt into a bowl and make a well in the centre. Put the butter in a small pan, add 200ml (7fl oz) water and bring to the boil. Remove from the heat, stir into the flour mixture and mix to a smooth dough. Cover and set aside for 10 minutes.
Lightly grease a 23cm (9in) spring form cake tin and place on a baking sheet. Cut off a third of the dough for the lid and press the rest into a round to line the tin, pressing it evenly up against the sides and over the rim.
Spoon the meats and mushrooms into the tin. Roll out the remaining pastry to make a lid, brush the edges with beaten egg and lift over the pie. Trim the edges and pinch together to seal. Decorate with pastry trimmings and pierce a hole in the centre.
Bake in the oven for 1½ hours, then remove from the oven and carefully release the sides of the tin. Brush the pastry with beaten egg and bake for a further 30 minutes. Leave to cool completely.
Heat the reserved stock gently with the rowan or redcurrant jelly, then whisk in the gelatine until it is dissolved. Leave until just beginning to thicken, then pour into the pie through the hole in the centre, using a funnel. Cool and chill, then slice and serve with a mixed salad or coleslaw.
This pie freezes well - simply assemble the pie and freeze before baking. Once you're ready to bake, simply throw it in the oven straight from the freezer.