Pulse the oats using a food processor until just about ground, but not too powdery. Add the flour, cocoa powder, cinnamon, baking soda and baking powder; pulse until just combined.

In the bowl of a stand mixer fitted with a paddle attachment, beat the butter, brown sugar, molasses, and vanilla at medium speed until light and fluffy, 2 to 3 minutes, stopping to scrape the sides of the bowl as needed. Add the eggs, one at a time, beating well after each addition.

With the mixer on low speed, add the oat mixture to the butter mixture in two additions, beating until combined after each addition. Cover the dough with plastic wrap and refrigerate for 30 minutes.

Preheat the oven to 350° and line a few baking sheets with parchment paper.

Scoop the chilled dough using a two tablespoon-sized cookie scoop, roll it into smooth balls and press it into 2-inch disks, about ½ inch tall. Place about 2 inches apart on the prepared baking sheets.

Bake until the edges are golden brown, but the centers are still a little shiny, 10 to 12 minutes. Let the cookies cool on the pan for 5 minutes, then move to a wire rack to cool completely.

For the icing: Whisk together the powdered sugar and water in a medium bowl until fully combined. If your icing is a little too stiff, feel free to add an extra teaspoon of water until the desired consistency is reached. Dip the tops of the completely cooled cookies into the icing, letting any excess drip off. Let sit for about 45 minutes, or until the icing has hardened.