Preheat the oven to 350ºF. Line 3 baking sheets with parchment paper or silpat liners.

In a large bowl, or the bowl of a stand mixer, combine the butter and both sugars. Beat until combined, about 60 seconds.

Add the eggs, molasses, and 1 teaspoon of the vanilla. Beat again until combined.

In another bowl, whisk together the flour, cinnamon, baking soda, nutmeg, and salt. Add this flour mixture to the bowl with the butter mixture and mix until combined.

Add the oats and mix until combined. The dough will be thick.

Using a cookie scoop, make balls about 1 1/2 tablespoons each and place 12 on each baking sheet. Use the heel of your hand to flatten the cookies to about 3/4” thick.

Bake cookies, one sheet at a time in the center of the oven, just until the edges start to brown, about 12 minutes. (12 minutes will give you a soft cookie. For a crispier cookie, cook around 15 minutes.)

Let the cookies cool completely.

To ice the cookies, combine the powdered sugar, the remaining 1/2 teaspoon of vanilla, and 3 tablespoons of milk. Whisk until combined, adding more milk as needed to make the icing the right consistency. You want it to flow off of the whisk, but you don’t want it too loose or it won’t coat the cookies.