For Cookies

1. Line a large cookie sheet with parchment paper. Set aside.
2. Place the butter in a medium saucepan over medium heat. Stir occasionally until butter has melted. Continue stirring often as butter begins to foam and crackle. Do not leave the butter unattended at this stage. Stir the butter as it sizzles and after about 4-5 minutes, bits of golden brown butter will fall to the bottom of the pan. The crackling sound will stop and the butter will be aromatic and amber in color. Do not brown the butter too much – we don’t want it dark, just golden.
3. Pour the butter into a large bowl. Be sure to scrape all of the brown bits from the pan. Set aside to cool for 20 minutes.
4. While the butter cools, pulse the oats in a food processor until they are a mix of fine crumbs (oat flour) and larger bits. Set aside.
5. In a medium bowl, whisk together the flour, baking soda, cinnamon, nutmeg and salt. Set aside.
6. Once the butter is cool to the touch, add the brown sugar and granulated sugar. Whisk to combine, about 1 minute. 
7. Add the eggs and vanilla, whisking to combine well. 
8. Add the molasses and stir to incorporate. 
9. Add the dry ingredients and the pulsed oats to the bowl and use a large spatula or wooden spoon to fold the ingredients together. Do not over mix.
10. Using a medium cookie scoop, divide the dough into uniform scoops and place on the prepared cookie sheet. Cover and chill overnight (or at least 3 hours).
11. Once the dough is chilled, preheat the oven to 350°F. Line two large baking sheets with parchment paper. 
12. Remove the cookie dough from the refrigerator and transfer the dough balls onto the lined cookie sheet, leaving about 2 to 3 inches apart. The cookies will spread a bit. Bake one sheet at a time in the center of the oven for 8 to 10 minutes. The cookies should be set on the edges and a light, golden brown. Do not over bake.
13. Remove the cookies from the oven and allow to cool on the cookie sheet for 5 to 10 minutes before carefully transferring to a wire cooling rack. Cool completely before adding the icing.

For Icing

In a medium bowl, mix all of the ingredients together and whisk until smooth and thick. The icing should not be thin and runny. If too thin, add more powdered sugar. 

To ice the cookies, carefully dunk the top of each cookie in the icing without submerging it completely. Allow the icing to drip off the cookies before flipping them over and placing on a wire rack to set. The icing will set in 2 to 3 hours.