Crisp edges, chewy center, pools of dark chocolate - this recipe combines what I consider to be the best elements from the Cook's Illustrated and the Jacques Torres recipes
Whisk both flours, baking powder and baking soda together in medium bowl; set aside.
180 g bread flour, 180 g cake flour, 4 g baking soda, 3 g baking powder
Place 224 g (16 tbsp) of the butter and the dry milk powder in a saucepan over medium-high heat until the butter is melted. Continue cooking, whisking constantly until the butter is dark golden brown and has nutty aroma (about 8 minutes, watch closely as the mixture can g o from golden to scorched very quickly). Remove pan from heat and stir the remaining 112 g (8 tbsp) of butter into the hot butter until completely melted.
336 g unsalted butter, 25 g dry milk powder
Add both sugars and salt to the pan with butter and whisk until fully incorporated. Add the egg, egg yolks and vanilla, whisk until mixture is smooth with no sugar lumps remaining, about 30 seconds. Let mixture stand 3 minutes, then whisk for 30 seconds. Repeat process of resting and whisking 2 more times until mixture is thick, smooth, and shiny.
150 g granulated sugar, 330 g dark brown sugar, 9 g salt, 15 ml vanilla, 1 egg, 2 egg yolk
Using rubber spatula or wooden spoon, stir in flour mixture until just combined, about 1 minute. Stir in chopped chocolate giving dough final stir to ensure no flour pockets remain.
510 g dark chocolate
Press plastic wrap against dough and rest in the refrigerator for at least 24 hours.
When ready to bake, remove the dough from the refrigerator and allow to sit at room temperature while preparing the oven and pans. Adjust an oven rack to the middle position and pre-heat the oven to 350°F. Line 2 large (18- by 12-inch) baking sheets with parchment paper.
Scoop the dough onto the prepared pans using a #30 (2 tbsp) cookie scoop. Bake until golden brown but still soft, about 12-14 minutes. Cool on the pan for a few minutes before removing to a wire rack to finish cooling. Store in an air tight container.
Notes
You can replace the bread and cake flour with an equal weight of all purpose flour. While this will alter the texture a bit, the cookies will still be delicious.
You can substitute chocolate chips for the chopped chocolate. If you do, I recommend using a variety of chip sizes/shapes. This will result in a "cleaner" appearance to the cookies as you won't have the tiny flecks of chocolate throughout the dough.
Experiment with other mix in options: different flavors of baking chips, nuts, M&Ms, etc.
You can make these cookies smaller if you like, using a #40 cookie scoop instead. If you do, reduce the baking time to about 10 minutes.
Because of the single egg, this isn't the simplest recipe to cut down. But if you do want to try, I would recommend whisking the egg until it is homogenous in color/texture and then splitting it in half. Typically, half of a large egg would be about 25 g.
When the dough comes out of the refrigerator, it will be very stiff. I strongly recommend that you do not skip allowing the dough to sit at room temperature for a while before attempting to scoop it.