Place hazelnuts on baking sheet. Bake until they're a shade darker and fragrant, about 10 to 15 minutes. Remove from oven and set aside to cool.
Lower oven to 325 degrees F.
Place hazelnuts in blender or food processor and pulse to coarse bits; set aside. Whisk together flour, baking powder, and salt to blend; set aside.
Beat butter and sugar together with a wooden spoon until smooth. Beat in egg. Gradually beat the flour mixture into the butter mixture. Add the chopped hazelnuts and mix until distributed evenly throughout.
Form into long cookies and place on greased cookie sheets. Bake until firm, about 15 minutes. Remove from oven and cool on racks.
In a saucepan over lowest heat or in a double boiler, melt chocolate. Dip 1 end of cooled cookies into melted chocolate. Place back on cookie sheet to harden.