Preheat the oven to 170°C. Butter the sides and line the bottom of a 20cm springform. Using a stand mixer, combine flour, sugar, margarine, eggs and a pinch of salt in a large mixing bowl until smooth, then toss in baking powder and give it a stir. In a small cup combine cocoa powder and hot milk to create a paste. Add to the batter and mix until combined. When ready, turn the mixture into the prepared tin and bake for 30-40 mins or until the skewer inserted into the middle of the cake comes out clean. Remove from the oven and cool for 5 minutes before turning out on to a wire rack. Take off the lining paper and leave the cake to cool.
Drain the cherries reserving the juice. In a small saucepan, mix cornflour with a small amount of juice until well combined, then add remaining juice. Place over a medium heat and bring slowly to the boil, stirring once in a while, until thickened. Taste and add some sugar if needed. Remove from the heat, add cherries (you can reserved a few to decorate top of the cake) and leave to cool.
Combine double cream, icing sugar and vanilla bean paste in a mixing bowl. Whip using a mixer until light and thick, then add cream cheese and mix until well combined.
When the cake is cold, cut it in half using a sharp serrated knife. Place one half on a plate and spread it with a 2/3 of the cream filling. Top with a cherry mixture. Place the other half of the cake on top, then spread remaining cream filling over it. Decorate the cake with chocolate shavings and a few cherries.