1. Preheat your oven to 350°F or 175°C. Line a baking sheet with a piece of parchment paper to prevent the cookies from sticking.

2. In a large mixing bowl, combine the flour, baking powder, sugar, and cocoa powder. In another bowl, take the butter and cream it until it becomes light and fluffy. Now add the syrup to the butter and mix until the two are well combined.

3. Gradually pour the dry ingredients from the first bowl into the butter mixture and mix everything together until just combined. Take the chopped hazelnuts and gently fold them into the mixture.

4. Now divide the dough into three equal sized pieces. Take each piece and shape it into a long thin log shape. Place the logs onto the prepared baking sheet, ensuring there is a little space between each one to allow for even baking.

5. Bake the logs in the preheated oven for 15 to 18 minutes. Check they are done by ensuring the edges are firm to the touch. Remove them from the oven and let them cool down slightly before cutting into bars while still warm.