Step 1: Prepare the Hazelnuts

1. Toast the Hazelnuts: Preheat your oven to 350°F (175°C). Spread the hazelnuts on a baking sheet and toast them in the oven for about 10-12 minutes, or until fragrant and lightly golden. Let them cool, then chop coarsely.

Step 2: Mix Dry Ingredients

1. Combine Dry Ingredients: In a medium bowl, whisk together the all-purpose flour, baking powder, and salt. Set aside.

Step 3: Cream Butter and Sugars

1. Cream the Butter and Sugars: In a large mixing bowl, using an electric mixer, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy, about 2-3 minutes.

Step 4: Add Egg and Vanilla

1. Incorporate Egg and Vanilla: Beat in the egg and vanilla extract until well combined.

Step 5: Combine Wet and Dry Ingredients

1. Mix Dry Ingredients into Wet Mixture: Gradually add the dry ingredient mixture to the wet mixture, mixing until just combined. Be careful not to overmix.

Step 6: Fold in Hazelnuts and Chocolate

1. Add Hazelnuts and Chocolate Chips: Gently fold in the toasted hazelnuts and milk chocolate chips until evenly distributed throughout the dough.

Step 7: Shape the Cookies

1. Scoop the Dough: Using a cookie scoop or tablespoon, drop rounded balls of dough onto a baking sheet lined with parchment paper, spacing them about 2 inches apart. If desired, sprinkle additional chopped hazelnuts on top of each cookie.

Step 8: Bake the Cookies

1. Bake: Preheat your oven to 350°F (175°C) and bake the cookies for 10-12 minutes, or until the edges are lightly golden and the centers are set.

Step 9: Cool and Serve

1. Cool: Allow the cookies to cool on the baking sheet for about 5 minutes before transferring them to a wire rack to cool completely.