Preheat the oven to 155'C.
Sift the ground almonds, the icing sugar and cocoa powder together.
Whisk the egg whites until white and fluffy and then add the caster sugar to the egg whites and continue whisking until you have stiff, glossy peaks.
Fold the ground almonds and icing sugar into the meringue mixture.
Cut and fold the mixture with a spatula until all of the dry ingredients are incorporated and the mixture is smooth, shiny and has reached the ribbon stage.
Spoon the mixture into a piping bag.
Pipe 2cm circles in straight lines across a baking sheet lined with a silicon paper. Leave a 1 cm gap between each macaroon shell. Drop the tray of macaroons onto the work surface from about 30 cm to remove any large air bubbles.
Use a sieve to sprinkle the rest of the cocoa powder over the macaroon shells. Allow the macaroons to rest at room temperature for 20 minutes or until the macaroon shells are no longer sticky to touch.
Bake in the oven for 15 minutes. If you are baking lots of macaroons you may need to keep the oven door slightly ajar (with a spoon or paper) to prevent steam building up in the oven. After 15 minutes, check the macaroons are cooked by gently lifting a macaroon at the edge of a tray. If the test macaroon does not stick, allow the tray of macaroons to finish cooking on the tray as it cools.
Allow the macaroons to cool completely before filling.
Chop the chocolate into small chunks, if necessary. Set aside in a heat-proof bowl.
Bring the double cream up to the boil. Remove from the heat and pour over the chocolate.
Leave to sit for a few minutes before stirring together until smooth.
Set aside until thoroughly chilled.
Use a piping bag or small spoons to fill the macaroons.
«The percentage of cocoa mass in the chocolate influences the chocolatey intensity of the ganache. However, avoid using an 80% chocolate, as it will be too bitter and the final product may be grainy. »