For the dough:

• Place the butter in a mixing bowl and whisk it together with the sugar and salt until it becomes creamy. Gradually add in the flour and crushed hazelnuts until homogenous.
• Cover the bowl with cling film and place in the fridge to firm up for 30 minutes.

For the filling:

• In a separate bowl combine the hazelnut flour with the sugar, vanilla sugar and cream until you get an even, moist filling.

Assembly and baking:

• Take the dough out of the fridge and preheat the oven to 180° C/ 356° F.
• Take two sheets of parchment paper and cut out two circles, the same diameter as the baking tray you'll be using (28 cm/ 10 inches) for the cake. We recommend using a springform tray because it will be easier to remove the cake when it's done, but you can use a tart tin too.
• Split the dough in half and roll out each half to be the same size as the circle cut out. Once you're done forming the dough layers, add the first layer at the bottom of the pan, then spread the filling on top leaving about 3 cm (1 ½ inches) from the edge. Moisten the outer edges of the dough layer with a little water and follow up with the second dough layer.
• Push the outer edges of the top layer downward using a fork to seal the cream inside.
• Place the cake in the oven and bake for 45 minutes. Once it's done, remove from the baking tray by removing the sides of the pan. Let the cake cool on a wire rack, then sprinkle with icing sugar.

Enjoy!