Note: This cookie dough requires a minimum of 3 hours of chilling, though I highly recommend chilling it overnight. The colder the dough, the easier it becomes to shape and handle during assembly.

Using a handheld or stand mixer fitted with a paddle attachment, beat the softened butter, granulated sugar, and brown sugar together in a large mixing bowl on medium-high speed for about 2–3 minutes, until the mixture is light and fluffy. Add the egg and vanilla extract, then continue beating on high speed until fully incorporated. Pause as needed to scrape down the sides and bottom of the bowl to ensure even mixing.

In a separate bowl, whisk together the flour, cocoa powder, baking soda, and salt until well combined. With the mixer on low speed, gradually add the dry ingredients to the wet mixture. Mix just until combined—the dough will be thick at this stage. Increase the speed to medium-high and mix in the milk, followed by the chocolate chips. The final dough will be sticky. Cover the bowl tightly and refrigerate the dough for at least 3 hours, or up to 3 days. Chilling is essential for this sticky dough to be workable.

When ready to bake, remove the dough from the fridge and let it sit at room temperature for about 10 minutes to soften slightly. Preheat your oven to 350°F (177°C) and prepare large baking sheets by lining them with parchment paper or silicone baking mats; set aside.

Scoop out about 2 tablespoons (40g) of dough and split it in half. Roll each half into a ball. Press a thumbprint or indentation into one of the halves and place a caramel candy inside. Take the other dough ball and place it on top, sealing the edges around the caramel to fully enclose it. Repeat the process with the remaining dough and caramels. Tip: Because the dough is sticky, it's helpful to wipe your hands clean after shaping every few cookies.

Place the assembled cookie dough balls on the prepared baking sheets, spacing them about 2–3 inches apart. Sprinkle the tops of each cookie with a pinch of flaky sea salt.

Bake the cookies for 12–13 minutes, or until the edges are set but the centers still appear slightly soft. Tip: If the cookies haven’t begun spreading by minute 9, remove the baking sheet from the oven and gently bang it on the counter 2–3 times. This helps encourage spreading. Return the sheet to the oven to finish baking.

Let the cookies cool on the baking sheet for 5 minutes. If desired, press a few extra chocolate chips into the tops while they’re still warm for a bakery-style finish—this step is purely for appearance. Afterward, transfer the cookies to a wire rack to cool completely. Note that the cookies may slightly deflate as they cool.

Store any leftover cookies in an airtight container at room temperature. They’ll stay fresh for up to 1 week.