In a medium mixing bowl, whisk together the all-purpose flour, Dutch-process cocoa powder, baking powder, and sea salt. Set this flour mixture aside for later use.

In a large bowl, use an electric mixer on high speed to cream the softened unsalted butter with the light brown sugar and granulated white sugar until the mixture is light and fluffy. This process ensures the cookies’ tender texture.

Mix in the egg yolks and 1 1/2 teaspoons of vanilla extract on medium speed for about 1-2 minutes until the batter becomes light and fluffy.

Gradually add the dry flour mixture into the wet mixture, mixing on low speed just until combined. Be careful not to overmix to keep the cookies tender.

Using a tablespoon-sized cookie scoop, portion out 32 balls of dough. Roll each into a ball, then press each one with a 1/4 teaspoon to create an indent. Chill the shaped dough balls in the refrigerator for one hour to firm up.

Preheat your oven to 350°F (175°C) about 15 minutes before baking to ensure it reaches the right temperature.

Arrange 12 cookies per large baking sheet lined with parchment paper. Bake for 9-11 minutes; around 10 minutes is ideal. As soon as they come out of the oven, lightly press the centers again with a 1/4 teaspoon to recreate the indents. Use a circular cookie cutter to perfect their round shape and reduce their size back to the original.

Let the cookies cool for 5 minutes on the baking sheet before transferring them to a wire rack to cool completely.

In a large saucepan over medium-low heat, add 1 cup granulated sugar. Heat gently, allowing the sugar to first crystallize then melt completely into a golden caramel, stirring occasionally. This process takes about 20 minutes. Reduce heat to low if crystals remain to avoid burning.

Once the sugar is melted and golden, immediately stir in 5 tablespoons softened salted butter until fully incorporated.

Slowly pour in 1/2 cup heavy cream while stirring quickly to combine. If the mixture separates, increase heat to medium-low and stir vigorously until smooth. Stir in 1 teaspoon vanilla extract and sea salt to taste (1/4 to 1/2 tsp).

Let the caramel sauce simmer gently on low for 2-3 minutes to thicken slightly, then remove from heat and allow it to cool completely before assembling the cookies.

Once the cookies are completely cooled, fill each center indent with a heaping teaspoon of the cooled salted caramel sauce. Optionally sprinkle a small pinch of sea salt on top before serving for added flavor contrast.