1. Preheat oven to 375°F. In a large, nonstick skillet, melt 1/2 cup of the butter over medium-high heat. Add the oats and cook, stirring, for 8 to 10 minutes, or until oats are lightly browned. Transfer to a bowl and let cool.
2. In a medium bowl, whisk together the flour, baking powder, baking soda and salt.
3. In a large bowl, use an electric mixer to beat the remaining 1/2 cup butter with the granulated sugar and brown sugar until light and fluffy, Scraping down the sides, as necessary. Add the egg, egg yolk, milk and vanilla, and mix until combined. Add the flour mixture and mix just until combined. Stir in the oats and chocolate chips.
4. Divide dough into balls (2 tablespoons each) and place on a large baking sheet, 2 inches apart. Press down on each ball to slightly flatten. Bake for 10 to 12 minutes, until slightly browned around the edges and centers look dry. Let sit on baking sheet for 2 minutes and transfer to a rack to cool. 

Note: Browning the oats gives them an extra buttery, nutty flavor and makes for an ultra-crispy texture.