Preheat oven to 180ºC (390ºF). Melt the butter in a saucepan over low heat. Set aside to cool slightly. Place the flour and sugar in a bowl and mix to combine. Add the butter, egg and vanilla and mix to combine. Stir through the hazelnuts and chocolate. Using your hands, mould 2 tablespoons of cookie mixture into a flat round and place on a baking tray lined with non-stick baking paper, leaving room to spread. Repeat with remaining mixture. Bake for 10–12 minutes or until golden. Allow to cool on trays. Makes 18.
* To check if the cookies are done, look at the bottom not the top. If you wait until the top looks right you risk overcooking them. To check, lift a cookie with a spatula so you can see underneath. The bottom should be deep golden. Cool on trays as the cookies will continue to cook after you’ve removed them from the oven.