Blitz the pistachios in a food processor or blender into fine crumbs. I used my nutribullet mixer.
100 grams Pistachio kernels (shelled and unsalted)
Tip the pistachio crumbs in a bowl and add the flour and salt. Whisk until well combined.
230 grams Plain flour, 1/4 teaspoon Salt
In a large bowl, beat the butter and sugar together until light and fluffy.
150 grams Unsalted butter, 120 grams Caster sugar
Mix in the egg and vanilla extract until smooth and combined.
1 medium Egg, 1 teaspoon Vanilla extract
Add the dry ingredients and mix everything together to make a smooth biscuit dough.
Flatten the dough into a disc and wrap in clingfilm. Place in the fridge to chill for 1 hour.
Lay a big sheet of greaseproof paper on a worktop and dust with flour. Dust your rolling pin with flour and roll out the dough to 0.5cm thickness. Use a Christmas tree cookie cutter to stamp out cookies. You will need to bring the scraps together again and re-roll the dough to stamp out 36 cookies in total.
Carefully transfer all of the cookies to baking trays lined with greaseproof paper, spacing them apart a little. Use a smaller Christmas tree cutter to stamp out the middle of half of the cookies (18 cookies). These are your "window" cookies.
Place back in the fridge for 30 minutes (or in the freezer for 15 minutes) to chill. Chilling the dough will help the Linzer cookies keep their Christmas tree shape.
Meanwhile, preheat the oven to 160°C fan / 180°C conventional.
Bake the Linzer cookies for 15 minutes, rotating the trays halfway through. Remove and leave to cool on the baking trays.
Spread the pistachio cream over the whole Christmas tree cookies.
150 grams Pistachio cream
Dust icing sugar over the "window" cookies.
Icing sugar
Place the "window" cookies on top of the pistachio cream cookies and lightly press down to sandwich them together. Enjoy!