Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a medium bowl, whisk together the flour, baking powder, salt, cinnamon, and nutmeg until evenly mixed.

In a separate large bowl, cream together the butter and brown sugar until light and fluffy, about 2-3 minutes.

Add the egg and vanilla extract to the butter-sugar mixture and beat until well combined, about 1 minute.

Gradually mix in the milk until the batter is smooth, about 30 seconds.

Slowly add the flour mixture to the wet ingredients, mixing on low speed until just combined, about 30 seconds.

Gently fold in the rolled oats and white chocolate chips until evenly distributed.

Scoop rounded portions of dough onto the prepared baking sheet, leaving about two inches between each cookie, and lightly flatten each scoop.

Bake the cookies for 10-12 minutes or until the edges turn golden brown.

Allow the cookies to cool on the baking sheet for about 5 minutes before transferring them to a wire rack to cool completely.