Preheat your oven to 350°F (175°C). Spread the hazelnuts on a baking sheet and toast them for 10-12 minutes until fragrant and golden brown. Once cooled, chop them roughly and set aside.

In a mixing bowl, whisk together the all-purpose flour, cocoa powder, baking powder, and salt until well combined.

In a separate bowl, beat the softened unsalted butter with granulated sugar and brown sugar for about 2-3 minutes until light and fluffy.

Add in the egg and vanilla extract to the creamed mixture, mixing until smooth. Gradually stir in the dry ingredients, then fold in the toasted hazelnuts.

Using a cookie scoop, scoop the dough into balls and flatten them slightly before placing on a lined baking sheet.

Bake the cookies for 10-12 minutes until edges are set but centers are still soft and chewy. Allow to cool on a wire rack.

Melt the semi-sweet chocolate along with coconut oil until smooth. Dip cooled cookie halves into melted chocolate, sprinkle with reserved chopped hazelnuts, and let cool until chocolate sets.