To make the pastry, whizz the flour, zest and butter in a food processor until combined. Add the beaten egg and pulse until it comes together. Wrap in clingfilm and chill for 10 mins.

On a work surface, roll out the chilled pastry in between 2 sheets of clingfilm to a circle large enough to line the bottom and sides of a 21cm tart tin. Line the tin with the pastry, gently pressing into the sides. Press small pieces of pastry into any cracks. Trim the edges and chill for 10 mins.

Preheat the oven to 190°C/170°C F/gas mark 5. Line the pastry case with baking paper and fill with baking beans. Bake for 10-15 mins, then remove the beans and bake for a further 10 mins until an even pale gold. Remove from the oven and set aside.

Reduce the oven to gas mark 4/180°C/160°C fan. Meanwhile, put the chocolate, butter, zest, mixed spice and cinnamon in a heatproof bowl set over a pan of simmering water and stir until the chocolate is completely melted. Remove from the heat and stir in the ground almonds.

In another bowl, beat the eggs and sugar with a hand mixer on high for 5 mins until the mixture is light and pale in colour, then fold into the chocolate mix.

Pour the filling into the tart case. Thinly slice the clementines and arrange the slices around the edge of the tart. Bake for 40 mins then remove from the oven, transfer to a wire rack and leave to set for 2 hrs. Dust with icing sugar to serve.