Prepare the brown butter as per the description above. Set aside to cool.
In a medium bowl, whisk together oats, all-purpose flour, whole wheat flour, baking soda, salt, ground cinnamon and baking powder.
Place brown butter in the bowl of a stand mixer with the paddle attachment.
Add the dark brown sugar and granulated sugar to the butter. Blend on medium speed until thoroughly combined, about 1 minute.
Add the egg and vanilla extract, mix until fully incorporated into the batter.
Transfer half of the dry ingredients into the batter. Mix on low speed until just combined.
Add in the remainder of the flour mixture. Mix on medium-low speed until well blended, about 2 minutes.
Mix in the chocolate chips. The dough will be soft.
Cover bowl and chill dough for at least an hour.
Preheat oven to 350°F.
Line two baking sheets with parchment paper.
Allow chilled dough to come to room temperature (about 5 minutes).
With a small ice cream scoop or a tablespoon, scoop even-sized balls of dough onto the prepared baking sheets spaced at least 2 inches apart. Roll the dough into balls; this will compact the dough making the cookie less likely to spread too thin.
Place back into the fridge to chill for about 10 minutes.
Place one of the baking sheets into the preheated oven and bake for 8 to 10 minutes. Edges will be set and the middles will look slightly underbaked.
Allow the cookies to cool on the baking sheet for 10 minutes (the residual heat will set the middles), before transferring cookies to a cooling rack to cool completely. Recipe from Redpath Sugar.
