oz/1 cup) brown 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, bicarbonate of soda and salt together into a large bowl. Place the sugar and butter in the bowl of an electric mixer and beat on medium speed for 1–2 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 buttermilk and beat until just combined, then beat in the vinegar, 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 frosting, place the cream cheese, butter and vanilla extract in the bowl of an electric mixer and beat on medium– high speed for 2–3 minutes or until combined and smooth. Reduce the speed, add the icing sugar and beat until combined. Cover with plastic wrap and refrigerate for 20–25 minutes or until firm.
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 15
225 g (8 oz/1½ cups) plain (all-purpose) flour
60 g (2¼ oz/½ cup) cocoa powder
1 teaspoon bicarbonate of soda (baking soda)
pinch of salt
160 g (5 oz/1 cup) brown sugar
125 g (4½ oz) unsalted butter, at room temperature
1 teaspoon natural vanilla extract
1 egg
250 ml (9 fl oz/1 cup) buttermilk
½ teaspoon white vinegar
CREAM CHEESE FROSTING
375 g (13 oz/1½ cups) cream cheese, at room temperature
75 g (2¾ oz) unsalted butter, at room temperature
1 teaspoon natural vanilla extract
125 g (4½ oz/1 cup) icing (confectioners’) sugar, sifted