Put the chestnut purée in a bowl and add the sugar and cream. Mix until you get a thick cream that’s easy to spread. (Add more cream if it’s too thick – but make sure the spread is not too runny!)
Roll out the puff pastry on a lightly-floured surface. Spread the chestnut cream evenly all over the pastry, then cover it with an even layer of mincemeat.
Roll it roll it up tightly like a Swiss roll. Wrap it tightly in clingfilm, then rest in the freezer for 15 minutes.
Preheat the oven to 180°C.
Remove the roll from the freezer and cut into 12 equal slices. Place these in a non-stick, lightly-greased scone or shallow muffin tin, cut-side facing upwards. Bake for about 15 minutes until golden.
Let the swirls cool in the tin, then remove them to a wire-rack with a spoon.
Dust them with icing sugar, then serve warm or at room temperature.