Directions:
Step 1: Preheat and Prepare Chocolate
- Preheat the oven to 375°F, placing a rack in the lowest position.
- Coarsely chop 1 cup of semisweet chocolate wafers, leaving some whole. Set aside.
Step 2: Mix Ingredients
- In a large bowl, mix together the dark brown sugar, granulated sugar, unsalted butter, and kosher salt until smooth (about 1 minute).
- Stir in the egg and vanilla paste/extract until the mixture is loose and resembles cake batter (about 30 seconds).
- Add the all-purpose flour and baking soda, mixing until the dough is uniform and streak-free (about 30 seconds).
- Fold in ¾ cup of the chopped chocolate, reserving the rest.
Step 3: Prepare the Skillet
- Transfer the batter to a 10" cast-iron skillet. If using a stainless-steel skillet, coat it with nonstick vegetable oil spray first.
- With damp hands, pat the batter into an even layer, extending to the sides of the pan.
- Scatter the remaining chocolate over the top and sprinkle with flaky sea salt.
Step 4: Bake
- Bake in the preheated oven until the edges are browned and slightly puffed, about 20–25 minutes (15–18 minutes if using stainless steel).
- Let the cookie cool in the skillet for 1 hour (if you can wait that long!).
Serving Suggestion:
- Serve the cookie warm directly from the skillet, or turn it out and cut into wedges. It pairs wonderfully with a scoop of vanilla ice cream.
Storage:
- Store any leftovers in an airtight container at room temperature. It's best consumed within 2-3 days for optimal freshness.