In a medium mixing bowl, whisk together all-purpose flour, Dutch-process cocoa powder, baking powder, and sea salt until combined.

In a large bowl, cream together unsalted butter, light brown sugar, and granulated sugar until light and fluffy.

Add egg yolks and vanilla extract to the creamed mixture, mixing until just combined.

Gradually add dry ingredients to the wet mixture, stirring until just mixed.

Scoop dough into 32 equal balls and place on a parchment-lined baking sheet, indenting each ball.

Chill dough in the refrigerator for at least 1 hour.

Preheat oven to 350°F (175°C) while dough chills.

Bake in the preheated oven for 9-11 minutes, checking for a set exterior.

In a small saucepan, heat heavy cream until simmering, then pour over chopped chocolate and stir until smooth.

Once cookies are cooled, spoon ganache into each indent.

Chill filled cookies in the refrigerator for 10-15 minutes to set.