To brown the butter, heat a thick-bottomed skillet on medium heat. Add the sliced butter, whisking frequently. Continue to cook the butter until melted. The butter will start to foam and browned specks will begin to form at the bottom of the pan. The butter should have a nutty aroma. Watch the butter carefully because it can go from brown to burnt quickly. Remove butter from the heat and let cool to room temperature.
In a medium bowl, whisk together the 2 cups Flour, 2 1/2 cups Oats, 1 tbsp Baking Powder, 2 tsps Cinnamon, 1/4 tsp Nutmeg, 1/8 tsp Cloves and 1 tsp Salt. Set aside.
Once the butter has cooled, in the bowl of a stand mixer combine the browned butter and the 1 1/2 cups Dark Brown Sugar. Mix together on medium speed for 2-3 minutes.
Add the 1 Egg, 1 Egg Yolk, 1 tbsp Plain Greek Yogurt, 4 tbsps Maple Syrup, and the 1 tsp Vanilla Extract. Mix together on medium speed for 4-5 minutes. It should be smooth and creamy.
Add all dry ingredients and stir until combined (no flour can been seen unmixed).
Cover dough with plastic wrap and place in the fridge to chill for 30 minutes to an hour.
Towards the end of the chill period, preheat the oven to 350 degrees Fahrenheit.
Measure about 2 tablespoons of dough and roll into balls. Flatten the ball slightly with the palm of your hand. Placing on a silicon or parchment lined baking sheet.
Bake the cookies 10-11 minutes or until the edges of the cookies begin to turn golden brown. The centers will still be soft. Don’t over bake. Cool the cookies on the baking sheet for 2-3 minutes, or until set. Transfer cookies to a wire cooling rack and cool completely.
While the cookies cool, whisk together the 1/2 cup Powdered Sugar, 1 1/2 tbsps Maple Syrup, and 1 tbsp Milk. Using a spoon drizzle the frosting over the cookies or simply use a knife to add a layer of frosting to each cookie.
Enjoy!