FOR THE COOKIES

• Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper or a silicone baking mat and set aside.
• In a large mixing bowl, using a hand mixer or a stand mixer fitted with the paddle attachment, cream together the room temperature butter, brown sugar, and granulated sugar until light and fluffy, about 2-3 minutes. Scrape down the sides and bottom of the bowl with a rubber spatula.
• Add the room temperature egg to the butter and sugar mixture. Beat on medium-low speed for 30 seconds until fully incorporated and the mixture is smooth.
• In a separate bowl, whisk together the all-purpose flour, cornstarch, rolled oats, cinnamon, nutmeg, baking powder, and salt.
• Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix. Scrape down the sides and bottom to ensure the mixture is evenly combined.
• Use a 3-tablespoon-sized cookie scoop to portion out the dough. Push two scoops of dough together to form larger cookies, making seven large cookies in total. In the palm of your hand, roll them into balls. Place 3-4 dough balls on the prepared baking sheet, spacing them about 3 inches apart.
• Bake in the preheated oven for 14-15 minutes, or until the edges are golden brown but the centers are still slightly soft. The cookies will continue to set as they cool. When the cookies are done baking, remove them from the oven. While they are still warm, use a flat spatula or the bottom of a cup to gently press the cookies down to about ½ inch thick. Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.
• In a medium bowl, whisk together the powdered sugar, milk, vanilla extract, and cinnamon until combined. If the mixture is too thin, add more powdered sugar. If it’s too thick, add a tiny bit of milk. A little goes a long way.
• Using a spoon, drizzle the icing on top of the cookies and let it set for at least 30 minutes before serving.