Preheat the oven to 225°F (110°C). Line a baking sheet with parchment paper and set it aside.
In a stand mixer, beat the egg whites until stiff. Gradually add the white sugar while continuing to beat until stiff peaks form.
Transfer the meringue batter to a piping bag and snip the end with a pair of scissors to create a 1/2-inch (1 cm) opening.
Pipe a dozen 1½-inch (3.5 cm) meringue circles onto the parchment-lined baking sheet, ensuring 2 inches (5 cm) of space between each. Top each meringue circle with one teaspoon of Nutella, then cover with the remaining meringue.
Bake for 20 minutes, then reduce the temperature to 170°F (76°C) and bake for an additional 40 minutes.
Remove the meringues from the oven and let them 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.