Preheat the oven to 200C/400F/Gas 6. To make the sweet pastry, rub the flour, butter, sugar and egg together with a splash of cold water until it just comes together as a dough. Do not over work the dough. Wrap the pastry in cling film and set aside to chill in the fridge while you make the filling.
To make the filling, turn the mincemeat out into a bowl, grate the zest of the tangerines into the mincemeat, then peel and chop the fruit. Throw the tangerine and apple pieces into the bowl and blend by hand.
Roll out the pastry to a 3mm/1/8in thickness. With a round pastry cutter, cut out 6 x 9cm/3½in discs of pastry. Press the pastry into the muffin cups and fill each one with a good helping of the mincemeat mixture, so that it reaches three-quarters of the way up the side of the pastry-lined cup.
With a fluted pastry cutter, cut out 6 x 8cm/3¼ in pastry circles for the lids (slightly bigger than the top of the muffin cups). Place a lid on top of each pie and gently push down. Sprinkle with caster sugar.
Bake for 20 minutes, then transfer to a wire rack to cool. Dust with icing sugar and serve warm with fresh cream.