Chocolate Marshmallow Whoopies

Ingredients

• 125g butter, at room temperature
• 160g (1 cup, lightly packed) brown sugar
• 1 tsp vanilla extract
• 1 egg
• 50g (1/2 cup) cocoa powder, sifted
• 1 tsp bicarbonate of soda
• 300g (2 cups) plain flour
• 330ml (1 1/3 cups) buttermilk

• Marshmallow filling

• 3 egg whites
• 270g (1 1/4 cups) caster sugar
• 2 tbs glucose syrup
• 1 tsp vanilla extract
• Pinch of salt

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.

Notes

• 
  Cook's tips: Make sure you use butter that's at room temperature - this helps aerate the mixture and makes it easier to incorporate the flour.
  If you don't have an ice-cream scoop, spoon tablespoonfuls of the mixture onto lined trays.
  Dip the ice-cream scoop or spoon into hot water, then dry, about every 10 scoops to easily get the mixture off the scoop. Don't do it too often or the mixture can become too wet.