Shortcrust pastry

1. Place the dry ingredients, flour, hazelnut meal, powdered sugar, baking powder, and salt in a large bowl.
2. Then add the cold butter cut into pieces and rub with your hands until you get a sandy texture.
3. Then add the egg and mix with a wooden spoon before finishing the mixture with your hands until it forms a homogeneous ball of dough.
4. Wrap the dough in plastic wrap and place it in the fridge for 20 minutes.
5. Then place the dough ball between 2 sheets of parchment paper and flatten it with a rolling pin to a thickness of about 3 mm.
6. Using a round cookie cutter (about 5 cm in diameter) cut out round shapes, remove the excess dough
7. Then place your cut-out cookies on a baking sheet covered with baking paper and put in the freezer for about 15 minutes.
8. Preheat your oven to 350°F / 180°C and bake the cookies for about 10 minutes for each tray.

 White chocolate ganache

1. Place the heavy cream with the white chocolate chips in a medium bowl.
2. And melt them in a double boiler on a saucepan containing a bit of water heated on medium heat, until you get a well-melted mixture. 
3. Cover with plastic wrap and place in the fridge until cool.

Assembly 

1. Fill a pastry bag with the cooled white chocolate ganache and fill a cookie with a small layer and place a second cookie on top to form a sandwich.
2. Place your filled cookies in the fridge for a few minutes to cool and harden the ganache.