125g butter, chopped
100g white chocolate, chopped
1 cup caster sugar
½ cup milk
¾ cup plain flour
½ cup self-raising flour
1 cup blackberries
250g butter, softened
3 cups icing sugar
Preheat oven to 160°C. Line a 12-hole ¹⁄₃-cup muffin pan with paper cases. Combine butter, chocolate, sugar and milk in a saucepan over low heat. Cook, stirring, for 5 minutes or until chocolate and butter have melted and mixture is smooth.
Remove from heat; set aside for 5 minutes to cool. Add egg; stir to combine. Add combined flours, mix.
Pour mixture evenly among the paper cases. Bake for 30 minutes or until a skewer inserted comes out clean. Transfer to a wire rack to cool.
To make blackberry buttercream, place berries in a small saucepan and cook over low heat until pulpy. Strain through a sieve, using the back of a spatula to press as much pulp through as possible. Return juice to saucepan. Cook, stirring, for 2 minutes or until it thickens. Set aside to cool.
Use an electric mixer to beat butter until very pale. Gradually add icing sugar, beating well between each addition. Add blackberry syrup; beat to combine. Place buttercream in a piping bag fitted with a 2cm fluted nozzle. Pipe onto cupcakes to serve.