Step 1

Prep the oven and pans. Position a rack in the center of the oven and preheat the oven to 350°F. Line two half sheet pans with parchment paper.

Step 2

Mix the dry ingredients. In a medium bowl, whisk together the flour, cinnamon, baking soda, and salt.

Step 3

Cream the butter and sugars, then add the egg and vanilla. In the bowl of a stand mixer fitted with the paddle attachment, combine the butter and sugars. Beat on medium-high until light, fluffy, and doubled in volume, 2 to 3 minutes, using a rubber spatula to scrape down the bottom and sides of the bowl as necessary. Reduce the mixer to low, add the egg and vanilla, and beat until combined. Scrape down bottom and sides of the bowl.

Step 4

Add the dry ingredients, oats, and chocolate. With the mixer on low, gradually add the dry ingredients and beat until just combined. Add the oats all at once and beat on low until combined, scraping down the bottom and sides of the bowl as needed to fully incorporate oats. Add the chocolate all at once and beat on medium-low until the chocolate is evenly distributed throughout, about 1 minute.

Step 5

Assemble the cookies. Use a 3-Tablespoon cookie dough scoop to portion the cookie dough into balls, placing them at least 3 inches apart on the prepared sheet pans.

Step 6

Bake the cookies. Bake one pan at a time for 15 minutes, or until the edges have set but the centers are still gooey. Cool the cookies on the pan on a wire rack for 20 minutes, or until the edges and bottoms of the cookies have set and feel firm to the touch. Repeat with the remaining cookie dough.

Step 7

Serve and store. Serve warm or at room temperature. The cookies can be stored in an airtight container or zip-top bag at room temperature for up to 3 days.