Preheat the oven to 200°C, gas mark 6 and grease a baking tray.
Lay the pastry out on a lightly floured work surface and cut into four 11cm (4 1/2 inch) rounds. Brush with the beaten egg, place on the prepared baking tray and bake in the preheated oven for 20 minutes until puffed and golden.
Put the shallots and wine in a saucepan, bring to the boil and continue to boil until the liquid has reduced by half. Add the cream and mustard and let it bubble away until it is thick enough to coat the back of a spoon.
Stir in the chopped fish and the prawns, add some salt and pepper to taste and cook for about 5 minutes until the fish is cooked through and the prawns have turned pink. Stir through the parsley and tarragon.
Spoon the fish mixture into serving bowls and top with the cooked pastry discs to finish.
Recipe courtesy of Lisa Faulkner.