Preheat an oven to 180°C/160°C fan/gas mark 4 and line a 23x33cm Swiss roll tin with non-stick baking parchment. It’s best to lightly grease the tin before lining so the parchment holds firm

In a large mixing bowl, preferably using an electric hand mixer, whisk the egg whites until they are stiff

In a separate bowl, whisk the egg yolks with the sugar and vanilla until pale and creamy. It may turn sandy at first, but keep whisking

Stir the flour, cocoa, baking powder and yoghurt into the egg yolk mixture. Fold in the egg whites with a metal spoon, trying not to lose too much air

Spoon the mixture onto the lined Swiss roll tin. Spread it out evenly

Bake for about 15 minutes until firm

Whilst the sponge is in the oven, dampen a clean tea towel. Lay it on the work surface, then put a sheet of baking parchment on top and finely grate about 10g of the dark chocolate over the surface

Allow the sponge to cool slightly in its tin, then upturn it onto the chocolate-covered parchment. Carefully remove the parchment it has been baked on. Don’t worry too much about the odd bit that sticks, leaving a little crater – this is the inside of the roll

Drain the cherries. Whip the cream until thick and stir in a little of the drained kirsch if you like. Feel free to add a little booze of your choice to the cream if your cherries were tinned or frozen

Spread the cream on the sponge, then arrange the cherries on top. You may need to squash any big cherries a little. Grate over a little more chocolate

Lifting the baking parchment, start to roll up the sponge from one of the short edges, coaxing it over itself until it’s rolled up fully and transfer to a serving plate or board. Keep in the fridge until you’re ready to serve

Finish with another grating of chocolate or a light dusting of icing sugar