Heat oven to 180C/160C fan/gas 4. Grease and line the base of 3 x 20cm cake tins. Boil the kettle. Put the butter and 75g chocolate broken into chunks in a small pan and gently heat, stirring, until completely melted.
Mix together the flour, sugar, cocoa and bicarbonate of soda with a pinch of salt in a mixing bowl. Whisk the eggs and buttermilk or yogurt together. Scrape the melted chocolate mixture and egg mixture into the dry ingredients, add 100ml boiling water and whizz briefly with an electric whisk until the cake batter is lump free.
Divide the mixture between the tins and bake for 25 mins, swapping the tins round after 20 mins if they’re on different shelves. To test they're done, push in a skewer and check that it comes out clean.
Prick the cakes a few times with a skewer. Mix together the 2 tbsp reserved cherry juice and the kirsch (or more juice) and drizzle over the cakes. Cool the cakes.
Mix together the remaining drained cherries and jam. Tip 200ml of the cream into a small pan and heat until just below simmering point. Chop the remaining chocolate and put in a heatproof bowl, pour over the hot cream and stir until melted. Set aside until spreadable.
When the cakes are cool whisk the remaining cream and the icing sugar together until softly whipped. Spread over two of the cakes, then spoon over the jammy cherries. Stack the cakes together. Spread the chocolate cream over the third cake and sit on top of the other cakes. Pile the fresh cherries in and around the cake and serve