This buttery cookie can be dipped in coffee for an afternoon treat.
Preheat oven to 350 degrees F. Lightly grease 2 cookie sheets; set aside. In a shallow baking pan, spread hazelnuts in a single layer. Bake for 10 minutes or until toasted, stirring once. Cool nuts slightly. Place the warm nuts on a clean kitchen towel. Rub the nuts with the towel to remove the loose skins. Finely chop nuts and set aside. Reduce oven temperature to 325 degrees F.
In a small saucepan, melt 1/4 cup of the butter over medium heat. Reduce heat to medium-low. Continue to cook, without stirring, about 5 minutes or until butter becomes brown and fragrant. Remove from heat; cool slightly.
In a large bowl, beat remaining butter with an electric mixer on medium to high speed for 30 seconds. Add granulated sugar, brown sugar, and 1/4 teaspoon salt. Beat until combined, scraping sides of bowl occasionally. Beat in browned butter and vanilla until combined. Beat in as much of the flour as you can with the mixer. Using a wooden spoon, stir in any remaining flour and the hazelnuts. Divide dough in half.
On each prepared cookie sheet, pat each half of dough into an 8-inch circle. Using your fingers or a fork, crimp edges of each dough circle. Prick every inch or so with the tines of a fork. Cut each circle into 8 wedges (do not separate wedges).
Bake for 15 minutes or until edges are lightly browned. Recut circle into wedges while warm. Cool on cookie sheet 5 minutes. Transfer wedges to a wire rack; cool.
In a small saucepan, combine chocolate and shortening. Cook and stir over low heat until melted and smooth. Dip scalloped edge of each wedge into chocolate, allowing excess to drip off. Return to wire rack. Sprinkle chocolate on wedges lightly with fleur de sel, if desired. Allow to stand until chocolate is set (about 1 hour). Makes 16 cookies.
Place wedges between sheets of waxed paper in an airtight container; cover. Store at room temperature for up to 3 days or freeze for up to 3 months.