Timmeh found this recipe in the online Detroit Free Press. He didn't directly ask me to make them, but I got the hint loud and clear.
(From and tested by Mary Spencer of Taste: A Cook's Place Northville MI)
1 cup all-purpose flour
1/3 cup Dutch process cocoa powder
1/2 cup unsalted butter, softened
2/3 cup sugar
1/4 teaspoon salt
1 egg yolk
2 tablespoons whole milk
1 teaspoon vanilla extract
1 cup finely chopped hazelnuts
1 egg white, lightly beaten
1/2 to 1 cup Nutella (hazelnut spread)
Toasted whole hazelnuts
In a small bowl, combine flour and cocoa powder; set aside. In a medium bowl, beat butter with an electric mixer on medium speed for 30 seconds. Add sugar and salt; beat until combined, scraping the side of the bowl occasionally. Beat in egg yolk, milk and vanilla until combined. Beat in the flour mixture. Cover and chill in the refrigerator for 1 hour.
Preheat the oven to 350 degrees. Grease 2 baking sheets or line them with parchment paper. Shape dough into 1-inch balls. On a sheet of waxed paper, place the chopped hazelnuts. Dip the balls in the egg white and roll in the chopped nuts. Place cookies 1 inch apart on a prepared baking sheet. Using your thumb, make an indentation in the center of each cookie. Bake for 10 to 12 minutes or until edges are firm.
Remove from oven and immediately use the rounded side of a 1 teaspoon measuring spoon to press down the center of each cookie. Transfer to wire racks and cool.
Once cool, spoon or pipe with a pastry bag fitted with a round tip a teaspoon of Nutella into the center of each cookie. Press a whole hazelnut on top.
Makes about 30 cookies
(I really did use my thumb)
(The small end of a mellon baller works well for making the indents after baking. They're a little fudgy in the centers)
(Two table knives work well for depositing the Nutella in the centers)