Preheat the oven to 375 degrees F and line two large baking sheets with parchment paper.
Add the sugars and butter to the bowl of a stand mixer. Mix on low and then increase to medium-high. Mix for about two minutes until pale yellow in color and smooth. Scrape the sides of the bowl.
Add the vanilla and then mix in the egg. Mix in the baking soda and salt. Next add the flour and mix on medium until a cookie dough forms, about 1 minute. Add the hazelnuts and then add the chocolate and mix on low for about 20 seconds to combine all ingredients.
Transfer the cookies in generous tablespoon portions to the baking sheets with no more than 12 cookies per tray. Sprinkle the top of each cookie with flaked sea salt. Bake each tray for about 10 minutes, until the cookies begin to brown at the edges and are firm in the center.
Let cool for 3 minutes on the tray and then transfer to a cooling rack to cool completely.
Recipe Courtesy of Oregon Hazelnut Marketing Board.