Preheat oven to 350°. Using a stand mixer if available, cream together butter and sugar until light and fluffy. Slowly add flour to creamed butter and sugar, mixing on low until fully incorporated, then mix in vanilla. Refrigerate dough until it’s easily handled and not too sticky to roll into a ball, approx. 30 min.
Line a 1/8 sheet pan (6 ½” x 9 ½”) with parchment paper. Press chilled dough into pan to form an even layer, covering the entire bottom of the pan. Smooth the top with the back of a metal teaspoon. Sprinkle chopped hazelnuts over the cookie dough, then press nuts into the top of dough with your hands. Bake approx. 20 min. When the top is light and golden, remove from the oven to cool a bit before slicing into bars or squares.
While cooling, melt chocolate chips in the microwave approx. 75 sec, depending on the power of your microwave. Chips should still be visible. Stir to complete the melting process.
Once cut cookies are fully cooled, dip into melted chocolate. Set cookie bars or squares on a parchment-lined cookie sheet and sprinkle with pink Himalayan salt. Chill for a few minutes in the freezer until chocolate sets, then serve.
Cookies can be stored in an airtight container for a week or in the freezer for up to 3 months.