Prepare the Dough: In a large bowl, cream together peanut butter, butter, granulated sugar, and brown sugar until smooth. Beat in the egg and vanilla. In another bowl, whisk together flour, baking soda, and salt. Gradually mix the dry ingredients into the wet ingredients until combined.
Add Hazelnut Swirl: Dollop hazelnut spread over the cookie dough. Sprinkle with roasted hazelnuts if using. Use a knife to swirl the spread and nuts into the dough gently.
Chill the Dough: Cover and refrigerate the dough for at least 1 hour.
Bake the Cookies: Preheat the oven to 350°F (175°C). Line baking sheets with parchment paper. Scoop tablespoonfuls of dough onto the prepared sheets, spacing them 2 inches apart. Bake for 10-12 minutes, or until the edges are golden but the center is still soft.
Cooling: Allow the cookies to cool on the sheet for 5 minutes before transferring to a wire rack to cool completely.