1. Turn the oven to 175°C (345°F).
2. Whisk the eggs, sugar and vanilla until white and really fluffy.
3. Melt the butter, add the sour cream and coffee and mix this into the eggs.
4. Mix the flour, baking powder, cocoa and salt and carefully fold this into the other ingredients.
5. Coarsely chop the chocolate and melt it in a water bath (in a bowl over boiling water). Mix this in to everything else.
6. Pipe or spoon out the mixture onto baking paper with a tablespoon.
7. Bake them in batches in the middle of the oven for about 10 minutes. Leave them to cool completely while you make the white chocolate frosting.
How to make the frosting
1. Chop the chocolate and melt it in a water bath (in a bowl over boiling water).
2. Whisk the chocolate with the cream cheese. Fill an icing bag with a round nozzle.
3. Pipe the frosting onto the underside of one cake and put it together with another cake (without frosting), like a macaron.
Hello Cupcake! by Leila Lindholm
Hello Cupcake! is a glorious little book about cupcakes and whoopie pies from Leila Lindholm - Sweden's answer to Nigella Lawson. Discover recipes for wedding cupcakes, After-Eight cupcakes, Miss Piggy cupcakes, lemon meringue whoopie pies and banoffee whoopie pies. Published by New Holland Publishers, priced £12.99.