Method

Preheat oven to 180C

Line two baking sheets with silicone paper or other non-stick baking liner and have a pastry bag with a plain tip (about 1/2-inch, 2 cm) ready.

Grind together the icing sugar with the ground almonds and cocoa so there are no lumps; use a blender or food processor since the ground almonds that you buy isn't quite fine enough.

Whisk the egg whites until they begin to rise and hold their shape. While whisking, beat in the granulated sugar until very stiff and firm, about 2 minutes.

Carefully fold the dry ingredients, in two batches, into the beaten egg whites with a flexible rubber spatula. When the mixture is just smooth and there are no streaks of egg white, stop folding and scrape the batter into the pastry bag (standing the bag in a tall glass helps if you're alone).

Pipe the batter on the parchment-lined baking sheets in 4 cm circles evenly spaced 3cm apart.

Rap the baking sheet a few times firmly on the work top to flatten the macarons, then bake them for 15-18 minutes. Let cool completely then remove from baking sheet.

CHOCOLATE FILLING

Place the chopped chocolate in a bowl that will hold all the ingredients.

Heat the cream in a small saucepan. When the cream just begins to boil at the edges, remove from heat and pour over the chocolate.

Let sit to allow the chocolate to melt.

Beat in the pieces of butter.

Let cool completely before using.

ASSEMBLY

Spread a bit of batter on the inside of the macarons then sandwich them together.

You may have some filling left over, save for some other choco moment.

Let them stand at least one day before serving, to meld the flavours and let the macaron soften.

Store in an airtight container for up to 5 days, or freeze. If you freeze them, defrost them in the unopened container, to avoid condensation which will make the macarons soggy.