Preheat the oven to 180°C/Gas mark 4. Take two 12-hole muffin trays and line 16 of the holes with paper muffin cases.
Melt the chocolate, butter and sugar together in a large heatproof bowl (make sure it’s large, as you will eventually add everything else to this bowl, too). Ideally, do this in a microwave on medium heat for 1 minute at a time, stirring at each interval, until all melted together. Alternatively, place the bowl over a pan of simmering (not boiling) water until the chocolate is melted and the ingredients are amalgamated. Allow to cool slightly.
Whisk the whole eggs and yolks, soured cream and vanilla extract together in a separate bowl.
Sift the flour and cocoa into a bowl and mix with a spoon until combined.
Add the egg mixture to the melted chocolate mixture and stir together with a spoon until amalgamated.
Gently fold in the flour mixture until all the dry flour and cocoa has been incorporated into the wet ingredients.
Spoon into the paper cases, around half full. Bake for 15–20 minutes until just firm. Test with a sharp knife to ensure they are cooked through. Allow to cool for 5 minutes then turn out onto a wire rack. Once cool, decorate as required.
To make the ganache, place all the ingredients together in a microwave-proof bowl and microwave on medium for 1 minute. Stir the mixture, then put back in the microwave and repeat the process until all the ingredients are melted together. Alternatively, you can place all the ingredients in a pan and heat gently, stirring often, until melted together.
Leave to cool slightly. The ganache is now ready to use.
To make the decoration, you will need a small amount of chocolate ganache in a piping bag with a No. 3 nozzle, 16 large chocolate-paste roses in bright multi-colours or chocolate shades if you prefer (alternatively, 16 sugar snowflakes cut from caramel-coloured petal paste with a plunger cutter, decorated with gold lustre dust or spray – great for Christmas!)
Make sure that once you have poured the chocolate ganache covering over your cupcakes, you leave them to set for a few hours, otherwise the decorations may sink into the topping.
When the ganache cake covering is set, pipe a small pearl of chocolate ganache onto the centre of each cupcake.
Attach the chocolate roses or snowflakes to finish.
Display on a large platter and serve as dessert at your party, or scoff them all by yourself.
Recipe courtesy of Juliet Sear's cookbook, The Cake Decorating Bible, available from Fancy Nancy.