Mix the dry ingredients: (flour, baking soda, and salt) then set aside.
Add the butter, peanut butter, eggs, sugar, and vanilla to a mix bowl, and beat on high until creamy. Mix in the dry ingredients, a third at a time, until completely incorporated.
Cover and move the dough to the refrigerator and chill for an hour.
Preheat the oven to 325F.
Roll the dough into small balls (~1 inch) in the palms of your hand, and put them on a greased cookie sheet (or use a silpat!).
Press the dough down with a fork with 2 perpendicular presses.
Bake for 12 minutes.
Wait at least 15 minutes until the cookies cool.
Smear a dollop of Nutella on the bottom of a cookie, and top with a second cookie to make a sandwich.