Preheat the oven to 375℉. Line 2 large baking sheets with parchment paper.

In a large bowl using an electric handheld mixer on medium speed, beat the softened butter, brown sugar, and granulated sugar for about 30 seconds. Add the egg, egg yolk, vanilla extract, and peanut butter and beat on high speed for 1 minute or until fluffy.

Whisk together the flour, baking soda, and salt. Add to the wet ingredients and mix on low speed until just combined.

Scoop the cookie dough, about 1 tablespoon of dough per cookie and roll into balls, placing 2 inches apart on the prepared baking sheets. Press a fork into the tops to create a criss-cross pattern and bake in preheated oven for 12-14 minutes or until lightly golden on the edges.

Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to finish cooling while you bake the remaining cookies. Enjoy!