Pour the hazelnut crumble in the bowl of the Stand Mixer (keep 2 tablespoons of this crumble aside to garnish the cookies with later on). Then add the brown sugar and the diced ice cold unsalted butter.

Attach the wire whip and lower the mixer head.

Select Speed 4 and mix the ingredients for 3 minutes until smooth. Then add the sifted pastry flour and baking powder. Season to taste with a pinch of the coarse salt.

Select Speed 2 and mix the ingredients for 3 more minutes until the hazelnut cookie dough comes together. It shouldn't be sticky but still be quite moist and smooth.

Then tilt the mixer head back up and remove the dough from the bowl. You don't need to knead it. Divide the dough up into even pieces. I ended up with a cookie dough weighing about 11 oz (330 g) which I divided into 11 even eggless hazelnut cookies.

Roll the dough into small balls. Put them on a baking tray lined with a piece of baking paper. Press them down a little using a spoon, a fork or a meat mallet. I used a cork from a wine bottle.

Now brush the top of the cookie dough with the milk.

Sprinkle with the hazelnut crumble you put aside in the beginning of this recipe.

Then bake the hazelnut cookies in a preheated oven at 356°F (180°C) for 20 to 25 minutes or until cooked through. Let them cool down fully at room temperature. They will still be soft but crisp up once cold. Then serve the cookies or store them in a large jar in a cool pantry for up to 3 days.