Chocolate & marshmallow whoopies

Method

• 1
  Preheat oven to 190°C. Line 2 baking trays with non-stick baking paper. Use an electric beater to beat the butter, sugar and vanilla in a bowl until pale and creamy. Beat in the egg.
• 2
  Stir in the cocoa and bicarbonate of soda to combine. Use a metal spoon to fold in flour and buttermilk, in alternating batches, until just smooth. The mixture should be a little stiff.
• 3
  Use a 3cm-diameter ice-cream scoop to place rounds of the mixture onto prepared trays, leaving 5cm for spreading. Use your finger to smooth mixture around the edges.
• 4
  Bake, swapping the trays halfway through cooking, for 10 minutes or until firm. Cool slightly. Place on a wire rack to cool completely. Repeat, in 2 more batches, with remaining mixture.
• 5
  To make the filling, whisk the egg whites, sugar, glucose, vanilla and salt in a heatproof bowl over a pan of simmering water for 10 minutes or until a ribbon trail forms when whisk is lifted.
• 6
  Transfer the marshmallow mixture to a clean bowl. Use an electric beater to beat for 5-8 minutes or until the mixture has cooled, is thick and holds it shape.
• 7
  Place whoopies, base-side up, on a clean work surface. Spoon the filling into a piping bag fitted with a 1cm fluted nozzle. Pipe filling onto half the whoopies, leaving a 2mm edge.
• 8
  Place the remaining whoopies on top and press lightly to sandwich together. Place the whoopies in the fridge until you’re ready to serve them.