Preheat your oven to 350°F / 175°C.
Line two large baking sheets with parchment paper.
In a medium bowl, whisk together the all-purpose flour, baking soda, and salt.
Set aside.
In a large bowl using a hand mixer or stand mixer, cream the room temperature butter, chunky peanut butter, brown sugar, and granulated sugar on medium speed until light and fluffy, about 2-3 minutes.
Beat in the egg and vanilla extract until just combined.
With the mixer on low, gradually add the dry flour mixture to the wet , mixing until just incorporated. Be careful not to overmix.
Fold in the chopped pecans with a spatula.
Roll the dough into 1. 5-inch balls (about 2 tablespoons / 30 ml / 1 fl oz each) and place them 2 inches apart on the prepared baking sheets.
Using the back of a fork, gently press down on each ball to flatten it slightly. Press again from the opposite direction to create the classic criss-cross pattern.
Bake for 10-12 minutes, or until the edges are lightly golden brown and the centers look slightly underdone.
Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely. Store in an airtight container at room temperature.
Do not overbake! For the perfect chewy texture, pull the cookies from the oven when the centers still look a little soft. They will continue to set on the hot baking sheet.
Chilling the dough for at least 30 minutes before rolling will prevent the cookies from spreading too much and will deepen the flavor.
