For the shells:
60g/2¼ oz egg whites
60g/2¼ oz caster sugar
7.5ml/1½ tsp egg white powder
120g/4¼ oz icing sugar
30g/1¼ oz ground almonds
20g/¾ oz ground macadamias, plus extra for sprinkling
For the filling:
80g/3¾ oz icing sugar
40g/1½ oz butter, softened
20ml/4 tsp Champagne
Line a baking tray with non-stick baking parchment. Fit a piping or pastry bag with a plain round tip.
Place the egg whites in a clean bowl, and sift the caster sugar and egg white powder over the egg whites. Whisk with an electric mixer until stiff peaks form.
In a separate bowl, sift together the icing sugar, ground almonds and macadamias. Add the egg white mixture to the almond mixture. Using a spatula, gently fold the mixture until the batter falls in ribbons when lifted with the spatula.
Fill the piping bag with the mixture and pipe 24 x 4cm/1½ in rounds on to the lined baking tray. Sprinkle half the piped shells with ground macadamias (these will be the tops).
Preheat the oven to 130ºC/250ºF/Gas 1⁄2. Leave the baking tray containing the macarons out in a warm, dry room for at least 15 minutes.
Place the tray in the middle of the oven and bake the macarons for 10 minutes. Remove from the oven and allow to cool.
To make the filling, place the icing sugar and softened butter in a large bowl, and whisk until crumbly. Add the Champagne and whisk until smooth and of a spreadable consistency.
To fill the macarons, place a teaspoonful of buttercream on to the flat side of an undecorated macaron shell and top with the flat side of a decorated shell. Repeat to make 12 macarons.
From The Perfect Afternoon Tea Recipe Book