To make the maple oatmeal cookies:

• Add the oats to the bowl of a large food processor and pulse 10-15 times, until you have a mixed texture of oat flour, some partially broken, and some whole.
• Combine the pulsed oats, all-purpose flour, baking soda, kosher salt, cinnamon and nutmeg in a large bowl and whisk to combine. Set aside for now.
• In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and brown sugar on medium speed until light and fluffy, about 2 minutes. Scrape down the sides of the bowl. Beat in the egg and egg yolk, one at time, scraping down the bowl again if necessary. Next, mix in the maple syrup and vanilla.
• Add the dry ingredients to the butter mixture in 2 separate additions, beating on low speed after each addition until the ingredients are just combined. Be careful not to overmix.
• Cover the dough and chill in the fridge for at least 1 1/2 to 2 hours*. In the meantime, preheat the oven to 350°F and line two baking sheets with parchment paper.
• Using a #50 spring-loaded cookie scoop, scoop the dough onto the prepared baking sheet, spacing about 3 to 4 inches apart (a #50 cookie scoop holds a little more than 1 tablespoon of dough). Bake for 12 to 14 minutes, until the edges are lightly browned (the centers will still look a bit soft and gooey). Allow the cookies to set on the baking sheet for 10 minutes before transferring to a wire rack to cool completely. Make sure the cookies are completely cool before icing.

To make the maple icing:

• Place the sifted powdered sugar, maple syrup, vanilla, kosher salt, and 2 tablespoons milk in a medium bowl and whisk to combine. Add more milk, 1 tablespoon at a time, until the icing is thick but thin enough to dunk the cookies in.
• Dunk each cooled cookie in the maple icing and place back on the wire rack to allow the icing to set, usually about 1 hour.