Preheat the oven to 225°F (110°C). Line a baking sheet with parchment paper; set aside.
In a stand mixer, beat the egg whites until stiff. Slowly add the white sugar and continue beating until stiff peaks form.
Transfer the meringue batter to a piping bag and snip the end of the bag with a pair of scissors to create a 1/2-inch (1cm) opening.
Pipe a dozen 1½-inch (3.5cm) meringue circles onto the parchment paper-lined baking sheet, making sure to leave 2 inches (5cm) in between each. Top each meringue circle with one teaspoon of Nutella, and then cover with the remaining meringue.
Bake for 20 minutes; then lower the temperature to 170°F (76°C) and bake for another 40 minutes.
Remove the meringues from the oven and leave to dry overnight.
Notes
When creating the meringue batter, if peaks do not form after incorporating the sugar, stand the bowl in a saucepan of hot water and beat for a few minutes.