Chocolate mousse tart with pistachio pastry

In a food processor, blend 80g of the pistachios to fine crumbs. Or chop finely then pass through a sieve.

Put the flour and 180g butter in a bowl and rub together with your fingertips until it resembles fine breadcrumbs. Stir through the pistachios and icing sugar until evenly distributed. Add the egg a little at a time and, using a dinner knife, mix until it forms a ball. Turn out onto a work surface and gently knead for 30 secs until it forms a dough. Cover with clingfilm and chill for 15 mins.

Meanwhile, preheat the oven to 180C/160C Fan/Gas 4.

Roll the pastry out between 2 sheets of baking paper lightly dusted with flour, to the thickness of a £1 coin. Use to line a 23cm loose-bottomed tart case. Line the pastry with baking paper, fill with baking beans or uncooked rice and bake for 15 mins. Remove the beans and cook for 5-8 mins until lightly golden.

Remove the baked pastry case from the oven, loosen the pastry to prevent it sticking and leave to cool completely in the case. Fill any cracks with leftover pastry.

Melt the chocolate and the other 65g butter in a heatproof bowl set over a pan of barely simmering water (don’t let the water touch the bowl).

In a separate bowl, whisk the yolks and 30g of the caster sugar until pale and fluffy. Stir through the chocolate.

Place the egg whites in a clean bowl and whisk until thick and stiff. Whisk in the remaining caster sugar.

Using a large metal spoon, gently fold the egg whites into the chocolate in 3 additions. Pour into the pastry case. Chop the other 20g of the pistachios and sprinkle on the tart. Bake on the middle shelf for 20-30 mins until risen and firm. Leave to cool completely before serving.