
Put the pistachios in a food processor and blitz to fine crumbs. Be careful to not blitz them for too long as they’ll start to turn into butter.
Add the blitzed pistachios to a large mixing bowl with the flour, sugar, baking powder and a pinch of salt. Mix everything until combined.
Next, add the cold butter and use your hands to rub it into the flour until it has a dry crumby texture. Lightly whisk the egg, then add it to the mixture. Use your hands to mix it in until it has a rough, rustic crumb texture.
Press just over half of the mixture into your cake tin (If you are using a non-stick spring form cake tin then there’s no need to grease it first as there’s enough butter in the pastry). Press it in, to form a even base layer.
Next, spread the pistachio cream over the top, making sure you keep about ½ inch border around the edge. If your pistachio cream is very thick, you can warm it up gently in a saucepan first.
Sprinkle the remaining pastry over the top of the cake in large crumbs. Place the cake in the fridge for at least 30 minutes.
Pre-heat the oven to 180C/350F fan (200C/400F static). Bake the cake for 30 minutes until it’s just starting to turn slightly golden on top.
Serve warm or at room temperature (delicious served with a morning cappuccino).