Just like any other cookie recipe, start by beating the room-temperature butter and brown sugar until smooth and creamy. Stop the mixer and scrape the bowl as needed.
1 cup Butter, 1½ cup Brown sugar
Add the eggs and yolk, one at a time and beat the mixture after each one. Add vanilla extract and mix well.
2 Eggs, 1 Egg yolk, 2 teaspoon Vanilla extract
Mix all dry ingredients, including the rolled oats and spices and add them to the butter mixture. Gently incorporate all the ingredients and scrape the bowl's bottom to mix everything well.
2 cups Quick rolled oats, 1¼ cups All-purpose flour, ¼ cup Whole wheat flour, 1 teaspoon Baking powder, ¾ teaspoon Baking soda, 1 teaspoon Cinnamon, ¼ teaspoon Nutmeg, ¼ teaspoon Salt
Cover the cookie dough and chill it in the fridge for an hour.
Preheat the oven to 350℉ and line two baking sheets with parchment paper or Baking Mat. Use an ice cream scoop to scoop about two tablespoons of the dough onto the baking sheet. Bake the cookies for 8-10 minutes or until the edges look set and slightly golden. Let them cool down on the baking sheet. Then, transfer them to the cooling rack and let them cool down completely before icing.
1¾ cup Powdered sugar, 2-3 teaspoon Milk, ½ teaspoon Vanilla extract