In a large bowl, mix together the flour, sugar and salt. Then blend in 1/2 cup softened butter using a pastry cutter. Then mix in the chopped hazelnuts so they're thoroughly incorporated. Form into a ball, cover with plastic wrap and refrigerate until well chilled, at least 1 hour.
Heat the oven to 375 degrees. On a floured surface, roll the dough to a thickness of about 1/8 inch and cut the cookies into hearts or rounds. They can get a little crumbly, so just press them back together and roll them gently.
Place the cookies on an ungreased baking sheet about one inch apart and bake 7 to 10 minutes or until barely browned. Then removed the cookies to a rack to cool completely
Once the cookies are cooled, spread Nutella on top, and place a second cookie on top to create a sandwich. Sprinkle lightly with powdered sugar and serve.
2.5 servings