For the macarons, process the icing sugar and nut meal in a food processor until very finely ground. Sift the mixture, discarding any leftovers.
Beat the egg whites until soft peaks form, gradually add sugar, beating well between additions until sugar has dissolved and mixture is glossy. Vigorously stir in the nut mixture in batches. The mixture should run slowly down the sides of the bowl when tilted. If the mixture is too firm, add a tiny bit more runny egg white.
Use a piping bag with a small (2cm) plain nozzle to pipe 4cm circles of the mixture onto baking paper lined trays. Stand the tray at room temperature for at least 1-2 hours, to form a glossy crust. Bake at 150°C for 15-17 minutes, until firm but not coloured. Cool completely before using a spatula to carefully remove from trays.
For the filling, heat the cream and coffee in a small saucepan until it is just simmering. Remove from heat and stir in chocolate until smooth and glossy. Refrigerate for 2 hours until firm and thick enough to spread. Sandwich macarons together with spoonfuls of ganache.
Tips & Hints:
Makes 20. Macarons will keep for 1-2 days in an airtight container. For chocolate hazelnut macarons, omit the coffee and use dark chocolate for the ganache. Sprinkle coffee over macaron shells before baking.