Preheat the 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 affixed, add cubed butter, brown sugar and granulated sugar
1 cup unsalted butter, ¾ cup dark brown sugar, ½ cup granulated sugar
Turn the 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. Once the butter sugar mixture starts to stick to the sides of the mixing bowl, it’s done
Turn the mixer to low and add egg and egg yolk then vanilla. Mix on medium for about 30-60 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 the mixer off, add in both flours, salt, baking powder and baking soda. Turn the mixer on low and stir until just combined. Do not over mix or you will have tough cookies rather than chewy cookies
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 and chopped heath bars, reserving the larger pieces of Heath bar for topping the cookies. Turn the mixer off and knead the dough a bit with your hands to ensure chocolate chips and Heath pieces are evenly incorporated.
1 cup semisweet chocolate chips, 1 ½ cups chopped Heath bars
Portion the dough into 2 ounce size balls, rolling between your palms to ensure a smooth ball. Place about 2 inches apart on the prepared baking sheets. Gently press a piece of chopped Heath bar into the top of each cookie
Bake in the 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.