In a stand mixer fitted with a paddle attachment, beat the butter for 1 minute on medium speed or until smooth and creamy. Add the powdered sugar and beat on medium speed until light and fluffy, about 1 minute. Beat in the egg and vanilla extract on high speed.
In a medium bowl, whisk the flour, cinnamon, nutmeg and salt until combined. With the mixer on low, slowly add the flour mixture and mix until just combined. Add 1 cup of the chopped hazelnuts and mix until just combined.
Place the dough out onto a floured work surface and divide into two halves. Use floured hands to shape each log into about 2 ½ inches in diameter and 8 inches long. Tightly wrap the logs in plastic wrap and place in the fridge for at least 4 hours or overnight.
Preheat oven to 350°F and line a baking sheet with parchment paper. Slice each log into 12 cookies, giving you 24 total. Place the cookies on the baking sheet about 2 inches apart and bake for 14-16 minutes or until the edges are browned and firm. Let cool for 5 minutes before transferring to a cooling rack.
Place the chocolate in a heat-proof bowl and microwave in 30 second intervals, stirring between each, until the chocolate is just melted. Dip each cookie halfway and place on parchment-lined baking sheet. Top with some chopped hazelnuts. Place the cookies in the fridge to let the chocolate set.
Notes
All refrigerated items should be at room temperature, which helps the dough mix easily and evenly.
Toast the hazelnuts as it draws the natural oils to the surface, intensifying the rich nutty essence, creating a deeper color, and making the hazelnuts crunchier.
Make sure all the cookies are the same thickness when slicing so they each bake in the same amount of time.
Use qualitychocolate as it contributes to the taste.