1Preheat oven to 180°C/160°C fan assisted. Line the bottom of a round 20cm springform cake tin with parchment paper then grease and flour the sides.
2Combine sugar and butter in a large bowl and beat until pale and fluffy, about 5 minutes.
3Beat in eggs one at a time, make sure to scrape the sides of the bowl after each addition, until combined and the mixture is pale and thick.
4Whisk together the self-raising flour, cocoa powder and salt then fold into the butter and egg mixture.
5Spoon batter into the cake tin and smooth the surface with a spatula or back of a spoon.
6Reduce heat to 170°C/150°C fan assisted and bake for 1 hour 30 minutes - 1 hour 40 minutes until cake is firm and a knife inserted comes out clean.
7Remove from oven and leave to cool in the tin for 10 minutes, then turn out and leave the cake to cool completely on a wire rack before assembling.
8To make the simple syrup, stir together warm water and caster sugar until dissolved. Stir in cherry liqueur, if using. Leave to cool.
9In a small bowl, mix together jam with cherry halves.
10Use a serrated bread knife to cut the chocolate cake horizontally into three.
11Place the bottom sponge layer on a serving plate and the other two on a large chopping board. Spoon or brush the syrup evenly over each sponge and leave to soak for about 3-5 minutes.
12To assemble, spread one-third of the whipped cream on the bottom cake layer then spoon over half of the jammy cherries. Carefully place the second cake layer on top, and repeat with half of the remaining whipped cream and last of the jammy cherries. Place the last cake layer on top and lightly spread with the remaining whipped cream. Decorate with shaved chocolate and cherries.
For the sponge
For the simple syrup
For the filling