In the bowl of a stand mixer with the paddle attachment, cream together the softened butter and brown sugar until fluffy, 3 to 4 minutes. Scrape down the sides of the mixer and add the egg and egg yolk; beat to combine. Then add the peanut butter and vanilla; beating until combined.
In a large bowl, whisk together the flour, baking powder, and baking soda. With the mixer on low speed, gradually add the flour mixture to the butter mixture. Beat until just combine. Cover and refrigerate for 1 hour.
Preheat the oven to 325°F and line a baking sheet with parchment paper. Using a cookie scoop, portion dough into balls and toss in granulated sugar. Place the dough 3 inches apart on the prepared pans. Press the tines of a fork on top of the cookies forming a crosshatch design.
Bake until light golden brown, about 14 to 16 minutes. Let the cookies cool on the pan for 5 minutes before transferring to wire racks to cool.
Notes
Peanut Butter
Avoid natural peanut butter in this recipe because it tends to make the cookies spread. I like to use a creamy peanut butter for the texture it gives the cookies. But if you love chunky peanut butter, it's delicious too!