To the bowl of a standup mixer, add the butter, sugars, and peanut butter. Beat on medium-high speed until fluffy and significantly lightened in color.

Add the eggs and the egg yolk one at a time, mixing until incorporated after each addition. Scrape down the sides of the mixing bowl and add the vanilla. Mix to incorporate.

Right on top of the wet ingredients, add the flour, baking powder, baking soda, salt, and cinnamon. Mix on low speed just until incorporated. Scrape down the sides of the bowl.

Add the oats and mix until just incorporated. Add the chocolate chips and mix until just incorporated.

Transfer the cookie dough to a large Ziplock bag and chill in the refrigerator for at least 1 hour or up to 3 days. Preheat the oven to 350 ℉ and line 2 cookie sheets (you might need more depending on the size of the cookie sheets) with parchment paper.

Remove the cookie dough from the refrigerator. Use your hands or a cookie scoop to form the dough into 2.5-inch balls. Arrange the dough balls on the prepared cookie sheets 2 inches apart. Bake for 14 minutes.

Allow the cookies to cool on the baking sheets for 5 minutes before transferring them to wire racks to cool completely.