Browning Your Butter

1. Place the sticks of butter in a medium saucepan over medium heat. Stir occasionally as the butter melts, foams, and begins to turn golden brown, about 8-10 minutes. Keep a close eye on the butter to avoid burning. When it smells nutty and turns amber in color, remove the pan from the heat.
2. Pour the browned butter, including any browned bits at the bottom, into your mixing bowl while you prepare the rest of the recipe.

Baking Your Cookies

1. Preheat the oven to 350°F (175°C).
2. Prepare the dry ingredients: Place the old-fashioned oats in a food processor or blender and pulse until finely powdered. Transfer to a large mixing bowl and add the flour (spooned and leveled), matcha powder, baking powder, baking soda, salt, and nutmeg. Sift or whisk to remove any clumps and set aside.
3. Combine the wet ingredients: In your mixing bowl where the brown butter is cooling, add brown sugar, white sugar, and vanilla extract. Beat on low speed to combine, then increase to medium speed and mix until smooth and creamy, about 2-3 minutes. Scrape down the sides of the bowl as needed.
4. Incorporate the eggs and dry ingredients: Add one egg to the wet mixture and beat until fully incorporated. Mix in half of the dry ingredients, then add the second egg and the remaining dry ingredients. Beat on medium speed until a cohesive dough forms, about 1 minute.
5. Fold in chocolate: If using, stir in the white chocolate chunks or chips with a spatula until evenly distributed.
6. Portion the dough: Use a cookie scoop or your hands to form golf-ball-sized portions of dough (about 2 tablespoons each). Place them onto ungreased aluminum baking sheets, spacing them about 2 inches apart.
7. Bake the cookies: Bake for 12-13 minutes, or until the edges are golden brown and the centers look just set.
8. Cool the cookies: Let the cookies cool on the baking sheet for 5 minutes, or until firm enough to handle, then transfer them to a wire rack to cool completely.