01 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
02 - In a medium bowl, whisk together flour, baking soda, salt, cinnamon, and nutmeg until well blended.
03 - In a large bowl, beat softened butter, brown sugar, and granulated sugar until creamy and light in texture.
04 - Add eggs one at a time, beating thoroughly after each addition. Mix in vanilla extract until incorporated.
05 - Gradually add dry ingredients to the wet mixture, mixing until just combined. Do not overmix.
06 - Stir in oats, raisins, and chopped toasted hazelnuts until evenly distributed throughout the dough.
07 - Drop rounded tablespoons of dough onto prepared baking sheets, spacing cookies 2 inches apart to allow for spreading.
08 - Bake for 10-12 minutes, until edges are golden brown and centers are just set.
09 - Let cookies rest on baking sheets for 5 minutes, then transfer to wire racks to cool completely before glazing.
10 - In a small bowl, whisk together powdered sugar, hazelnut spread, and milk until smooth and pourable. Adjust consistency with additional milk if needed.
11 - Drizzle the hazelnut glaze over cooled cookies using a fork or piping bag. Allow glaze to set before serving.