Separate the egg whites in a clean bowl and wrap it with a cling film. Keep it on the kitchen counter for 24-48 hrs or in the fridge for 5 days. Before starting bring the egg whites to room temperature.
Beat the egg whites in a stand mixer or a beater. While beating add the granulated sugar little by little and beat it well. Beat till its stiff and shiny peaks form.
Grind the almond meal, cocoa powder and icing sugar together and sift this, discard the large chunks. Now add the almond mixture into the beaten egg whites.
Fold in with a spatula slowly till all the dry ingredients are fully incorporated in the egg whites. This is called macronage and the batter should not be under mixed or over mixed.
The texture of this batter, should be like when we lift the spatula, the batter should fall down in thick ribbons and the peaks will disappear in 10 to 15 seconds.
These will be shiny. (It is said like 40 to 50 strokes. For me it was done in between 40 to 45 strokes). Now fill the batter in a piping bag with plain round tip.
Line a baking sheet with parchment paper and pipe out small rounds on it. Tap the baking sheet on kitchen counter for several times to knock out the air. Keep these shells to rest for 20 to 30 minutes till a thin film appears on the shells.
Preheat the oven at 140 degree Celsius for 20 mins. Bake the macarons at 140 degree Celsius for 15 to 18 mins. Bake one tray at a time.
After the macarons are done allow it to cool completely. Peel out the shells carefully.
For the filling, boil the cream in a sauce pan. Put the chopped white chocolate in a bowl and pour the boiled cream over this. Mix it well.
Let it cool down. Now fill this ganache in a piping bag. Pipe out some cream on one shell and sandwich with another shell.