Inside Out Chocolate Chip Cookies

In a large mixing bowl, beat the softened butter with brown and granulated sugars on medium speed until pale and fluffy, about 3 minutes.
With the mixer on low, add in the egg, egg yolk, and vanilla extract. Mix until well blended (it may look slightly curdled—this is fine).
In a separate bowl, whisk together the flour, cocoa powder, baking soda, and salt until well combined.
Using a spatula or wooden spoon, gently fold the dry ingredients into the butter mixture until just combined and streaks of flour remain.
Add 1 cup of the white chocolate chips and fold in just until distributed and no dry flour remains. Do not overmix.
Cover the bowl and chill the dough for at least 3 hours (or up to 3 days) in the refrigerator.
When ready to bake, preheat your oven to 350°F (175°C). Line baking sheets with parchment paper. Let the chilled dough sit at room temperature for 10–15 minutes to scoop more easily.
Roll or scoop dough into 1.5-tablespoon size balls and place on the prepared baking sheets, leaving 2–3 inches between cookies.
Bake for 10–12 minutes, until the edges are set and the centers look slightly underbaked.
Remove from the oven and immediately press the remaining 1/2 cup of white chocolate chips gently onto the tops of the hot cookies.
Let cookies cool on the baking sheet for 5–10 minutes before transferring to a wire rack to finish cooling.