Preheat oven to 350ºF.
Spread the hazelnuts in a single layer on a baking sheet. Bake 10-12 until toasted. Transfer to a food processor or balnder and pulse until ground but not pasty.
Place flour and salt in a small bowl, stir to combine.
In a large bowl combine sugar and butter with an electric mixer until light and fluffy, scraping down the sides of the bowl. Beat in egg and vanilla. Gradually add in flour mixture. Beat in hazelnuts at low speed until well blended.
Place dough on a sheet of waxed paper and roll it back and forth to form a log 12” long x 2-1/2” wide. Wrap log in plastic wrap and refrigerate until firm, at least 2 hours or overnight.
Preheat oven to 350ºF. Cut dough with knife crosswise into ¼” slices. Place cookies 2” apart on ungreased cookie sheets. Bake 10-12 minutes or until edges are lightly browned. Let cookies stay on cookie sheets for 1 minute before removing to wire racks to cool completely.
Melt chocolate chips in a 2 cup glass measuring cup or microwave safe container on high for 2 minutes, stirring until smooth.
Dip each cookie ½ of the way up to coat. Let excess drip back into cup. Transfer cookies to waxed paper; let stand until set, about ½ hour.