1 Preheat oven to 150°C (300°F). Place the butter, brown and caster sugars in an electric mixer and beat until pale and creamy. Add the eggs, one at a time, and beat until combined. Add the flour, cocoa and baking powder and mix until combined.
2 Roll tablespoonfuls of the mixture into balls+ and place on baking trays lined with non-stick baking paper, allowing room to spread. Flatten slightly and bake for 15–20 minutes or until light golden. Cool on wire racks.
3 To make the pink marshmallow icing, place the marshmallows and butter in a saucepan over low heat and stir continuously until smooth. Remove from heat, add the chocolate and stir until melted and smooth. Allow to cool completely.
4 Spread half the biscuits with the icing and sandwich with remaining biscuits. Roll the sides of the whoopie pies in the sprinkles to serve. Makes 14.
+ The dough is very sticky, so use damp hands when rolling into balls. The dough results in a soft, cake-like biscuit.