Prep the Nutella centers. Line a baking sheet with parchment. Scoop Nutella into 3/4–1 teaspoon mounds.
Freeze for at least 30 minutes, until firm.
Heat the oven. Preheat to 350°F (175°C). Line two baking sheets with parchment paper.
Cream the butter and sugar. In a bowl, beat softened butter and 1/2 cup powdered sugar until smooth and creamy, about 1–2 minutes. Mix in vanilla.
Add dry ingredients. Stir in flour and salt until just combined.
If using nuts, fold them in now. The dough should be soft but not sticky.
Portion the dough. Scoop tablespoon-sized balls. Flatten each slightly in your palm to create a small disk.
Fill and seal. Place a frozen Nutella nugget in the center of each disk.
Wrap the dough around it and pinch to seal. Roll gently into a smooth ball.
Bake. Arrange on the prepared sheets with a little space between them. Bake 12–14 minutes, until the bottoms are lightly golden but the tops are still pale.
First sugar coat. Let cookies cool for 5 minutes, then roll warm cookies in powdered sugar.
This helps the sugar stick.
Cool and second coat. Once fully cool, roll again in powdered sugar for that classic snowy finish.