Start by melting 1 cup of unsalted butter in a medium saucepan over medium heat, until it turns golden brown and releases a nutty aroma, about 5-7 minutes.

Pulse 1 cup of old-fashioned oats in a food processor until you have fine crumbs and larger bits, then transfer to a large mixing bowl.

In the bowl, pour in cooled brown butter, 3/4 cup granulated sugar, and 3/4 cup brown sugar, blending until smooth and creamy, about 2-3 minutes.

Add in 2 large eggs and 1 tablespoon of pure vanilla extract, blending until fully incorporated.

Stir in 1/4 cup of molasses until well blended.

In a separate bowl, whisk together 1 3/4 cups all-purpose flour, 1 teaspoon baking soda, 1 teaspoon ground cinnamon, 1/4 teaspoon ground nutmeg, and 1/2 teaspoon salt.

Fold the dry ingredients into the wet mixture, then add the pulsed oats, mixing gently until just combined.

Portion the dough into 2-tablespoon balls, place on a lined baking sheet, cover, and chill in the fridge for at least 3 hours or ideally overnight.

Preheat your oven to 350°F (175°C) and bake the chilled dough balls for 9-10 minutes until puffy and slightly golden.

Allow cookies to cool for 5-7 minutes on the baking sheet before transferring to a wire rack to cool completely, then dip in icing once cooled.