Crispy crunchy oatmeal cookies

1. 1. Heat oven to 350 F and arrange a rack in the middle of the oven. Line two baking sheets with parchment paper.
2. In a medium bowl, whisk together the flour, baking powder, baking soda, salt and cinnamon. Set aside.
3. In a bowl of a standing mixer, cream the butter and the two sugars until light and fluffy, 3 to 5 minutes. Scrape down the sides of the bowl, add the egg and beat until incorporated, about 30 seconds. Scrape down the bowl and do the same with the vanilla.
4. On low speed, add the flour mixture and beat until just combined. Remove the bowl from the mixer and fold in the oats by hand, mixing just until there are no remaining flour pockets.
5. Form balls out of tablespoon-sized pieces of dough and place them 2 inches apart on the parchment-lined cookie sheets. Bake one sheet at a time for about 15-19 minutes, rotating once for even cooking. Let the cookies cool completely on the baking sheets for maximum crispness. The cookies will keep in an airtight container for a week.