For the meringue: In a saucepan, combine the sugar and water. In a mixing bowl, add the egg whites and beat at high speed. Once the syrup reaches 260°F (126°C), pour it over the egg whites while continuing to beat until the mixture cools.

For the shells: In a mixing bowl, combine the almond flour, powdered sugar, cocoa powder, and egg whites. Gradually fold in the Italian meringue using a spatula.

Transfer the mixture to a piping bag and pipe the macarons onto a baking sheet lined with parchment paper. Bake at 340°F (170°C) for 12 minutes.

For the chocolate ganache: In a bowl, whisk together the egg yolks and sugar until pale. In a saucepan, bring the milk to a boil and pour it over the chocolate, stirring to melt. Add the egg yolk and sugar mixture, and mix well. Chill in the freezer for one hour.

Once the shells have cooled, pipe the ganache onto half of the shells, then top with the remaining shells. Chill in the freezer for 30 minutes before serving.