Preheat the oven to 200ºC, fan 180ºC, gas 6. Mix together the mincemeat, cranberries and orange zest in a bowl.
Lay the puff pastry out on a floured work surface, with the longest edge facing you. Spoon the mincemeat along the centre in a strip about 5cm wide, leaving about 2 cm of pastry free at each end. Brush the pastry edges with the beaten egg, then carefully lift the long edge nearest to you over the mincemeat and roll tightly like a big cigar. Seal each end, then transfer onto a baking tray and place in the fridge to chill for 30 minutes.
Cut 4 or 5 small slits in the top, brush with the beaten egg then bake for 25-30 minutes, until golden.
Put it on a serving platter, dust with icing sugar and serve with the crème fraîche.
Cook’s tip: this mince pie puff is delicious served with vanilla ice cream, brandy butter or custard.