cup) caster (superfine) sugar Preheat the oven to 175°C (340°F/Gas 3–4). Grease and flour 2 baking trays or 3 whoopie pie tins. Sift the flour, cocoa and bicarbonate of soda together into a large bowl. Place the sugar and butter in the bowl of an electric mixer and beat on medium speed for 2–3 minutes or until light and creamy. Add the vanilla extract and egg and beat for a further minute. Reduce the speed and add the flour mixture, in 3 batches, alternating with the milk and beat until combined, scraping down the sides of the bowl as required.
Place 1½-tablespoon amounts of batter about 5 cm (2 inches) apart on the trays and bake for 8–10 minutes or until cooked through. Cool for 5 minutes on the trays, then transfer to wire racks to cool completely.
Meanwhile, to make the buttercream, place the eggwhite and sugar in the top of a double boiler over medium heat and whisk for 3–4 minutes or until warm and the sugar has dissolved. Remove from the heat. Using electric beaters, beat the mixture on medium–high speed for 6–7 minutes or until glossy and stiff peaks form. Reduce the speed and add the butter, 1 cube at a time, beating well after each addition. Continue to beat for 2–3 minutes. Combine the melted chocolate and cocoa. Add to the eggwhite mixture and beat to combine.
Transfer to a piping bag fitted with a 1 cm (½ inch) plain nozzle and pipe 2 tablespoons of filling onto half of the cookies. Sandwich with the remaining cookies.
MAKES 12
150 g (5½ oz/1 cup) plain (all-purpose) flour
60 g (2¼ oz/½ cup) cocoa powder
½ teaspoon bicarbonate of soda (baking soda)
145 g (5¼ oz/ cup) caster (superfine) sugar
90 g (3¼ oz) unsalted butter, at room temperature
1 teaspoon natural vanilla extract
1 egg
250 ml (9 fl oz/1 cup) milk
CHOCOLATE BUTTERCREAM
3 eggwhites
145 g (5¼ oz/ cup) caster (superfine) sugar
160 g (5 oz) unsalted butter, cubed and at room temperature
125 g (4½ oz) dark chocolate (65% cocoa solids), melted
2 tablespoons cocoa powder