1. First, make the sponge. Preheat the oven to 180 degrees, and line a 20x30cm tin with baking paper. Whisk the eggs and sugar – either in a stand mixer with the whisk attachment, or with a hand-held mixer – for five to eight minutes, until voluminous. Sift the dry ingredients into a separate bowl and then use a whisk to gently fold in the egg mixture.
2. Pour into the prepared tin and use a palette knife to level the top. Bake for 10-12 minutes until springy to the touch.
3. For the crème diplomate, first place the milk and vanilla in a saucepan, and heat over a medium heat until it almost comes to the boil. Meanwhile, place the eggs, flour and sugar in a separate bowl and whisk thoroughly to combine. Slowly pour the hot milk over the egg mixture, whisking all the time. Then decant this back into the saucepan, and heat over a low heat, whisking constantly, until it has thickened, and just started to bubble. Pour this over the chopped chocolate in a heatproof bowl, and whisk until the chocolate has melted.
4. Place into a container with cling film pressed on to the surface to prevent a skin from forming. Allow to set in the fridge for at least an hour.
5. When you are ready to assemble, gently fold the whipped cream into the cooled and set custard.
6. For the jelly, place the frozen fruit in a bowl. Then heat the sugar and water in a saucepan until the sugar has dissolved. Boil for one minute, then pour over the fruit. Allow to sit for 30 minutes to let the fruit defrost, and to infuse the syrup. Strain out the fruit from the syrup, reserving both (the syrup is for the jelly, and the fruit is for assembly).
7. Soak the gelatine leaves in cold water for five minutes, to soften. Place about half of the syrup in a saucepan and heat until steaming. Remove the gelatine from the cold water, squeezing to remove excess liquid. Place this into the hot syrup, and whisk to combine. Pour this mixture back into the remaining syrup, and mix thoroughly. Allow this jelly to cool to room temperature.
8. To assemble: cut the sponge into pieces and fit them neatly into the bottom of the trifle bowl. Spoon the reserved fruit into the bowl (saving some cherries for garnish on top), and pour the rum over the top. Pour in the crème diplomate, and use a palette knife to smooth over the surface.
9. Place this in the fridge for 30 minutes to set (this will prevent the jelly from leaking into the bottom). When the crème diplomate has set, and the jelly is cool, pour the jelly over the top. Place back in the fridge to set fully (at least two hours, or overnight).
10. When it has set, whisk the cream with the vanilla and the icing sugar to soft peaks. Spoon this over the top of the trifle, using the back of a spoon to create little peaks and swoops. Dust with cocoa powder and dot with reserved cherries.

* Note on gelatine: you can use leaf or powdered gelatine, but make sure you check the package for the quantity needed. You should have about 600ml of syrup, and the package will tell you how much gelatine is needed to set this.