In a medium mixing bowl, whisk together the flour, cocoa powder, baking powder, and sea salt. Set aside.

In a large bowl, cream the butter, brown sugar, and granulated sugar together with an electric mixer on high speed until light and fluffy.

Add in the egg yolks and vanilla, mixing on medium speed until light and fluffy, about 1-2 minutes.

Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined.

Scoop the dough into 32 portions using a tablespoon-sized cookie scoop. Roll each portion into a ball, then press the center with a ¼ teaspoon to create an indent. Chill the dough balls for one hour.

Preheat the oven to 350°F. Arrange the chilled dough balls 12 per parchment-lined baking sheet.

Bake for 9-11 minutes (10 minutes for chewier cookies).

Immediately after baking, press the centers again with a ¼ teaspoon if needed. Use a circular cookie cutter to shape the cookies into perfect circles while they are still hot. Allow the cookies to cool on the baking sheet for 5 minutes, then transfer them to a wire rack to cool completely.

Add the granulated sugar to a large saucepan and heat over medium-low. Stir continuously as the sugar melts and turns golden in color. This process takes about 20 minutes.

Once the sugar has melted and turned golden, add the butter immediately and stir quickly until incorporated.

Add the heavy cream and stir quickly again to combine. If the mixture separates, increase the heat slightly and stir vigorously until combined.

Stir in the sea salt and vanilla extract. Let the caramel simmer on low for 2-3 minutes, then remove from heat and let cool completely.

Once the cookies are completely cooled, fill each indent with a heaping teaspoon of caramel sauce.

Sprinkle sea salt on top of the caramel and serve!