1.Combine flours, baking powder, bicarb, hazelnuts and 1 teaspoon of the salt in a medium bowl.
2.Whisk sugars, oil and 1/3 cup (80ml) water in a large jug until smooth.
3.Add sugar mixture to flour mixture and stir until combined. Place in freezer for 30 minutes or until mixture is firm.
4.Preheat oven to 180°C (160°C fan-forced). Line two large oven trays with baking paper.
5.Using a trigger ice-cream scoop, scoop level balls of dough 5cm apart onto prepared trays.
6.Bake cookies for 12 minutes or until golden around edges. Remove from oven. Place chocolate chunks over cookies. Return trays to oven for 3 minutes or until chocolate is melted. Sprinkle with remaining salt flakes. Cool on trays for 10 minutes. Transfer to a wire rack to cool. Suitable to freeze.
If the weather is hot and humid store these cookies in an airtight container in the fridge Cookie dough can be made up to 2 weeks ahead; keep in an airtight container in the freezer. Roasting and skinning hazelnuts from scratch gives much more flavour than the pre-roasted variety. Make this recipe vegan by using vegan-friendly chocolate.