Preheat oven to 400ºF (if you have convection, turn it on). Line two baking sheets with parchment paper or silicone baking mats.
In the bowl of a stand mixer with paddle attachment, add cubed butter, brown sugar and granulated sugar.
1 cup unsalted butter, ¾ cup dark brown sugar, ½ cup granulated sugar
Turn mixer on low for a few seconds, then gradually increase speed to medium-high, mixing for about 3-4 minutes until well incorporated and fluffy.
Turn mixer to low and add egg and egg yolk then vanilla. Mix on medium for about 30 seconds until well incorporated, stopping to scrape down the sides and bottom with a rubber spatula, as needed.
1 large egg , 1 large egg yolk, 1 ½ tablespoons vanilla extract
With mixer off, add in both flours, salt, baking powder and baking soda. Turn mixer on low and stir until just combined. Do not over mix.
1 cup cake flour, 1 ½ cups all-purpose flour, 1 teaspoon baking powder, 1 teaspoon baking soda, 1 teaspoon kosher salt
Add in chocolate chips. Turn mixer off and knead dough bit to ensure chocolate chips are evenly incorporated.
2 ½ - 3 cups semi-sweet chocolate chips
Portion dough into 2 ounce size balls, rolling between your palms to ensure a smooth ball. Place about 2 inches apart on prepared baking sheets
Bake in preheated oven for 4-5 minutes if using convection (7-8 minutes in conventional oven) then rotate baking trays and bake for another 4-5 minutes for convection (7-8 minutes for conventional).
Allow to cool for a few minutes on trays then transfer to wire racks.