In a large bowl, whisk together the cake flour, adjusted bread flour, baking soda, baking powder, and salt.
2 cups cake flour (Minus 2 tablespoons), 1 ⅔ cups bread flour, 1 ¼ teaspoon baking soda, 1 ½ teaspoon baking powder, 1 ½ teaspoon fine sea salt
In another bowl (or stand mixer), beat the butter, brown sugar, and granulated sugar together until light and fluffy, about 3–4 minutes.
1 ¼ cups unsalted butter, 1 ¼ cups light brown sugar, 1 cup granulated sugar
Beat in the eggs one at a time and the vanilla extract, scraping down the sides as needed. Stir in the vanilla.
2 large eggs, 2 teaspoon pure vanilla extract
Slowly add the dry ingredients to the wet, mixing until just combined. Fold in the chocolate discs or chunks.
1 ¼ lbs bittersweet or dark chocolate discs or chunks
Scoop the cookie dough into 3.5 oz portions (about ¼ cup) and place them on a baking sheet lined with parchment paper. Cover the whole tray with plastic wrap or transfer the dough balls to an airtight container, then refrigerate for 24–72 hours. Chilling them already portioned makes baking later so much easier and helps the cookies bake more evenly.
Preheat oven to 350°F. Place the chilled cookie dough balls on parchment-lined baking sheet and bake for 15–18 minutes, or until golden around the edges but soft in the center.
Let cookies cool fully on a wire rack before moving to the next step.
Melt your extra dark or bittersweet chocolate gently (in a double boiler or microwave in 20-second bursts). Once smooth, flip each cooled cookie upside down and spread a layer of melted chocolate on the bottom.
8 oz bittersweet chocolate chunks or disks
Place the cookies chocolate-side-down on a parchment-lined baking sheet and refrigerate or let sit at room temp until the chocolate firms up.
For that salty-sweet finish, hit the tops of the cookies with a pinch of flaky sea salt.
Flaky sea salt