Place egg in a bowl and beat it with a spoon or whisk.
Add 1/2 cup of the Nutella and beat until smooth. Stir in 1/2 cup of the flour. Slowly stir in remaining flour; batter will be thick and sticky.Drop 9 rounded tablespoons of batter onto a parchment lined cookie sheet, leaving about 2 inches of space.
Bake for 10-12 minutes.
Let cool for at least 10 minutes. Carefully cut cookies horizontally through the center; fill each with a rounded teaspoonful of Nutella. Chill cookies
