Peanut Butter Oatmeal Chocolate Chip Cookies

Preheat the oven to 350°F. Line large baking sheets with parchment paper.
In a medium bowl, whisk together the flour, baking powder, baking soda, salt, and cinnamon (if using). Set aside.
In a large bowl, use an electric mixer to beat the butter, peanut butter, granulated sugar, and brown sugar on medium-high speed until light and fluffy, about 2 to 3 minutes. Beat in the eggs, egg yolk, and vanilla, one at a time, beating well after each addition. Scrape the bottom and sides of your bowl with a spatula in between each addition. Slowly beat in the flour mixture until just combined. Add in the oats and chocolate chips until just combined.
Using a large spring-loaded scoop, drop 3-tablespoon sized balls of dough onto prepared baking sheets. Flatten slightly with the bottom of a measuring cup.
Bake for about 12 minutes, or until the edges are slightly browned, rotating baking sheets halfway through. Let the cookies cool on baking sheets for 5 minutes before removing to wire racks to cool completely. Cookies can be stored in an airtight container at room temperature for up to 3 days.