1. In a medium bowl whisk together the all-purpose flour, unsweetened cocoa powder, baking soda, and fine sea salt until well combined and free of lumps.

2. In a large mixing bowl beat the softened unsalted butter, brown sugar, and granulated sugar together until light, creamy, and slightly fluffy.

3. Add the egg and mix just until combined, then beat in the egg yolk, vanilla extract, and milk until the mixture looks smooth and glossy.

4. Add the dry ingredients to the butter mixture and mix on low speed or by hand just until no dry flour streaks remain, being careful not to overmix.

5. Cover the bowl and chill the dough in the refrigerator for 30 to 45 minutes, or until it feels firmer and easy to scoop.

6. Preheat the oven to 350°F (175°C) and line two baking sheets with parchment paper.

7. Scoop about 1 1/2 tablespoons of dough, flatten it slightly in your palm, place one soft caramel candy in the center, and wrap the dough fully around the caramel, pinching the seams closed.

8. Roll the filled dough into a smooth ball and place it on the prepared baking sheet, spacing cookies about 2 inches apart; repeat with the remaining dough and caramels.

9. Bake the cookies for 9 to 11 minutes, or until the edges look set and the tops are puffed and slightly crinkled but the centers still look soft.

10. Immediately sprinkle the warm cookies with flaky sea salt, then let them cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool further or enjoy warm and gooey.