Preheat the oven to 180°C.
Melt the butter, then let it cool.
Meanwhile, cut the stack of pastry sheets into 10 cm squares. Cover them with a tea towel.
Lightly butter a shallow muffin or tartlet tin.
Lay a filo square on a chopping board, brush it with butter then layer another square on top, turned through 45°C. Brush this with butter then layer another square on top, again angled. Repeat once more, so you'll have 4 sheets of filo making a star shape.
Put this star into one of the tin holes, slightly pushing it down with your fingers.
Make more filo stars with the rest of the pastry squares. You should have 8 tarts.
Put the tin in the oven and cook for 10 minutes until crispy and lightly golden.
Take the tin out of the oven, fill each tartlet with 1 teaspoon of mincemeat and a few cranberries. If the pastry is brown, cover the tin with foil.
Bake for another 5 minutes or until the cranberries are soft the pastry is golden.
Let the tartlets rest in the tin for 5 minutes, then transfer them to a wire rack to cool.
Dust with icing sugar (perhaps mixed with cinnamon) just before serving.