Whisk both flours, baking powder, soda and salt in a medium bowl.

Scrape butter into a large bowl and add both brown sugar and granulated sugar. Whisk until butter is absorbed into sugar, about 30 seconds. Add egg and then egg yolks, one at a time, whisking to combine after each addition. Whisk in vanilla.Mixture should look much lighter in color and be almost creamy.

Add dry ingredients and use a rubber spatula or wooden spoon to stir until just incorporated and almost no dry streaks remain. Set aside a handful of chocolate then add remaining chocolate and nibs (if using) to batter. Cover and chill for 2 hours, but I chilled overnight.

Place racks in upper and  lower thirds of oven. Preheat to 375. Line 2 baking sheets with parchment paper. Using a tablespoon, scoop out 2-Tablespoon portions of dough and place 5 on each baking sheet, spacing evenly. Roll into balls and press a few reserved chocolate pieces into tops of cookies. Cover and chill remaining dough.

Bake cookies, rotating cookie sheets top to bottom and back to front halfway through baking, about 4 - 5 minutes. Let bake another 4 -5 minutes until edges are golden brown and centers are puffed for a total time of 8 - 10 minutes. Pull baking sheets out of oven and tap cookie sheet on counter to deflate cookies. Sprinkle with Maldon sea salt or Diamond salt if you used it.

Let cookies cool on baking sheets for 5 minutes, then transfer to wire racks to cool completely. Let baking sheets cool and repeat with remaining dough to make 6 - 8 more cookies.