Making the hazelnut dough

Fit the K-Beater.

Add ground hazelnuts, butter and sugar into the appliance bowl.

Mix for about 2 minutes on speed 3 until combined.

Add flour.

Mix for about 2 minutes on speed 3 until a dough has formed.

Add water if the dough hasn’t started to come together.

Mix for about 1 minute on speed 2 until a smooth dough has formed.

Transfer the dough to a work surface and knead lightly.

Form the dough into a disc and wrap in plastic wrap.

Chill in the fridge for 2 hours.

Making the pistachio dough

Clean the appliance bowl and fit the K-Beater.

Add ground pistachios, butter and sugar into the appliance bowl.

Mix for about 1 minute on speed 2 until combined.

Add flour and food dye, if using.

Mix for about 1 minute on speed 2 until the dough has formed.

Add water if the dough hasn’t started to come together.

Mix for about 1 minute on speed 2 until a smooth dough has formed.

Transfer the dough to a work surface and knead lightly.

Form the dough into a disc and wrap in plastic wrap.

Chill in the fridge for 2 hours.

Line two baking trays with parchment paper.

Take about 10 g of the dough, roll into a ball and place on the baking tray.

Repeat the same process with the remaining dough, keeping the flavours separate and spacing the biscuits 2 cm apart.

Cover the trays with plastic wrap.

Chill in the freezer for 30 minutes.

Preheat the oven to 180ºC.

Bake the biscuits for 15 minutes at 180ºC, until the edges start to crisp.

Transfer to a cooling rack and let cool completely.

Spread a little melted chocolate on each hazelnut biscuit.

Wait for about 2 minutes for the chocolate to start setting.

Sandwich the biscuits together and place on a serving plate.

Spread pistachio paste on half of the pistachio biscuits.

Top with the remaining biscuits and place on a serving plate.

Serve.