Preheat oven to 375º F. Line baking sheet with parchment paper, set aside.
In a bowl, whisk together flour, salt, and baking soda. Set aside.
With a stand mixer fitted with a paddle attachment, combine sugar, brown sugar, butter, and peanut butter. Beat until combined and fluffy. Scraping down sides when necessary.
Add egg and vanilla. Continue beating until mixed. Then add the flour mixture and beat until combined.
Scoop a full tablespoon of dough and roll into 1 inch balls. Place balls 11/2 inches apart.
Bake for 10 to 12 minutes then remove from oven and immediately press with the back of a spoon for the thumbprint. Cookies will crack when you press—this means you did it right! Place on wire rack and let cool.
Transfer Nutella to a piping bag fitted with a tip. Fill thumbprints with Nutella. Alternatively, you can spoon the Nutella in to the thumbprint.
Store in an airtight container.
This recipe doubles and triples easily. The dough can be stored in the freezer for up to a month.