Preheat the oven to 300 F (150 C).
Prepare 4 baking sheets by lining them with parchment paper.
Finely grind the almond powder and 250g of icing sugar, this mixture is called tant pour tant.
Sift this mixture and remove the pieces of almond powder that are too large to pass through the sieve.
Add the remaining 200g of icing sugar and cocoa, then mix well.
Beat the egg whites and tighten with sugar 2 to 3 times.
Pour the dry ingredients over the beaten egg whites and mix using a spatula, making sure to scrape the bowl.
Macaronage, this is the moment when you need to check if you get a ribbon.
Pour the batter into a pastry bag.
Form squares of batter on the parchment paper.
Let it rest for 30 minutes.
Bake for 15 to 20 minutes.
After baking, slide the parchment paper onto a cold surface and let cool before removing the shells.
Heat the cream until it boils, then pour it over the white chocolate chips.
Wait 1 minute before mixing until you get a smooth and homogeneous texture.
Add the balsamic vinegar and mix.
Let it cool completely before filling the macarons.