- Preheat the oven to 350°F (180°C). Line the bottom of a 9-inch (23 cm) springform pan with parchment paper but do not grease the sides of the pan.
- For the cocoa sponge, warm the whole eggs (including the eggs for the yolks) in a bowl of hot water for about 2 minutes to warm them up. Crack the eggs and separate the 2 yolks into a large mixing bowl or the bowl of a stand mixer. Add the sugar and using electric beaters or the whip attachment, whip the eggs until they triple in volume and hold a ribbon when the beaters are lifted, about 6 minutes (you can’t overwhip, so if in doubt, whip one more minute.)
- Sift the flour and cocoa powder together. Add this while mixing at medium-low speed to blend in quickly. Spoon about ½ cup (125 mL) of the batter into a bowl and stir the melted butter into this. Add this back to the larger bowl and whisk in by hand. Scrape the batter into the prepared pan and gently spread to level it, if needed.
- Bake the cake for about 45 minutes, until it springs back when gently pressed. Cool the cake in its pan on a rack completely. To remove the cooled cake from the pan, run a palette knife around the inside edge of the pan before removing the springform ring.
- For the chocolate custard, whisk the egg yolks, sugar and cornstarch with ½ cup (125 mL) of the cold milk in a bowl and set aside. Bring the remaining 2 ½ cups (625 mL) of the milk to just below a simmer over medium heat. Add the chocolate and whisk in. Pour this over the egg yolk mixture while constantly whisking. Return the custard to the pot and, still over medium heat, whisk until the custard becomes thick and glossy and just a few bubbles break the surface as it starts to simmer.
- Transfer the custard to a food processor,blender or use an immersion blender, add the vanilla and cream cheese and pulse this until the cream cheese is fully combined. Transfer the custard to a bowl, cover and chill for at least 3 hours before assembling.
- For the cherries, bring the cherries, sugar and cinnamon up to a full simmer over medium-high heat and cook for about 15 minutes, until the liquid reduces a little and the cherries are rosy pink. Whisk the cornstarch with enough water to liquefy it and add this to the pot, stirring until the cherries return to a full simmer and the liquid thickens, about a minute. Remove the pot from the heat, cool the cherries to room temperature and chill completely before assembling.
- For assembly, prepare the simple syrup by bringing the sugar and water to a full simmer, stirring until the sugar dissolves. Stir in the vanilla (it can be used warm). Whip the cream and skim milk powder until it holds a soft peak and whisk in the icing sugar. Chill this until ready to use.
- To assemble the trifle, dice up the cake into 1 ½-inch (3.5 cm) cubes. Arrange an even layer in the bottom of your trifle bowl. Brush a generous amount of simple syrup over the cake. Spoon the chilled chocolate custard into a large piping bag (no tip required) and pipe this over the cake in an even layer. If using the fudge filling, dollop little spoonfuls of it on top, checking that it is visible through the glass of the trifle bowl. Spoon the cherry filling over this and repeat, layering the cake, chocolate custard, fudge filling and cherries until you almost reach the top of the bowl. Spread the whipped cream on top and top with chocolate shavings. Chill until ready to serve.