Heat the oven to 200°C (180° fan) 400°F gas 6.
Place paper cases in a 12 hole bun tin.
Beat the mascarpone, vanilla and half the sugar until smooth and chill.
Whisk the egg whites with the salt until stiff.
Beat the egg yolks with the remaining sugar in a mixing bowl until thick and creamy.
Sift in the espresso powder, flour, cornflour and baking powder and fold in thoroughly.
Stir the melted chocolate into the mascarpone.
Pour the mascarpone mixture into the flour mixture and mix thoroughly.
Fold the beaten egg whites into the mixture until incorporated.
Spoon into the paper cases and bake for 20-25 minutes until risen.
Cool in the tin for a few minutes then place on a wire rack to cool completely.
Heat the cream, add the white chocolate, stir until dissolved and chill until thickened.
Beat the chocolate topping until creamy.
Spoon into a piping bag and pipe onto the cupcakes.
Decorate with shredded coconut.
Chill until ready to serve.