Preheat oven to 350 degrees. Line 2 cookie sheets with parchment paper, set aside.
Beat butter with electric mixer on medium speed for 30 seconds. Add brown sugar and beat until combined. Beat in egg yolk, vanilla, and salt. Beat in flour on low speed until dough comes together. Stir in chocolate.
Shape dough into 24 1 1/4 inch balls. Arrange 2 inches apart on cookie sheet. Use your thumb to make indents in each ball. Fill with 1/2 tsp hazelnut spread.
Bake 10 minutes or until edges are lightly brown. Cool on wire racks.