Instructions: Warm the oven up to 350F 175C and put parchment paper on a baking sheet. Put peanut butter, white sugar, and brown sugar in a bowl and mix them together until they are well mixed. Together with the vanilla extract and egg, mix the peanut butter until it is smooth. Mix the flour, baking soda, and salt together in a different bowl. Slowly add the dry ingredients to the peanut butter mixture and mix them in until they are just combined. Take dough balls about the size of a tablespoon and roll them into balls. Set the dough balls about 2 inches apart on the baking sheet that has been prepared. Make a hole in the middle of each cookie with your thumb or the back of a teaspoon. Put the cookies in an oven that is already hot for 10 minutes. Take the cookies out of the oven and, if necessary, gently make the holes bigger. Cool the cookies for a few minutes on the baking sheet, then move them to a wire rack to cool all the way down. After the cookies have cooled, heat the Nutella in a bowl that can go in the microwave for 15 seconds at a time, stirring each time, until it's smooth and just a little runny. Carefully put warm Nutella into the holes in each cookie. Before you serve or store the cookies, let the Nutella set.