For the pastry place the flour and sugar in the largest bowl of the food processor and pulse quickly to combine. Add the butter and process to fine breadcrumbs. Add the egg yolk and 1 tbsp of water and process until the mixture forms a ball, if mixture is dry add remaining tbsp of water.
Remove the pastry from the food processor and gently knead the pastry into a disc, wrap in cling film and chill for 30 minutes minimum.
Pre-heat the oven to 180C. Remove the pastry from the fridge, roll out and line a 23cm oblong or round fluted tin with a loose base.
Pierce the base of the pastry with a fork, line with greaseproof paper and fill with baking beans. Bake for around 15 minutes until the pastry is set. Remove the baking beans and return to the oven for around 3 minutes to dry out.
For the filling, process the pistachios in the smallest bowl of the processor until very fine. Sieve, retaining any larger lumps for decoration.
Measure 75g of the ground pistachios into a separate bowl and then add the ground almonds and flour.
Place the butter and sugar into the medium bowl of the processor and process until creamy. Add the eggs one at a time, processing between each addition to ensure they are fully combined. Finally add the pistachios, almonds and flour and process until combined.
Spread the base of the pastry shell with the apricot jam, and then carefully top with the pistachio and frangipane filling. Sprinkle with the reserved pistachios and bake in the oven for approximately 25 minutes or until the filling has set and the top is golden brown.