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

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

In a large mixing bowl, beat softened unsalted butter, granulated sugar, and brown sugar together until light and fluffy, about 2-3 minutes.

Add egg and vanilla extract to the butter-sugar mixture, blending until smooth and well incorporated.

Gradually mix in the dry ingredients until just combined, then gently fold in the chopped toasted hazelnuts.

Using a cookie scoop or tablespoon, roll dough into balls and flatten lightly. Place on a lined baking sheet.

Bake for 10-12 minutes until edges are set but centers remain soft. Cool on a wire rack.

Melt semi-sweet chocolate and coconut oil in a microwave-safe bowl until smooth. Dip each cooled cookie halfway into the chocolate and sprinkle reserved chopped hazelnuts on top.