Start by preparing 6-8 small cake rings. Place them on a board or baking tray lined with parchment paper and line them with acetate sheets.
Mix the graham crackers, butter and vanilla in a bowl. Spoon 1-2 tablespoons of this mixture into each cake ring and press well with your fingertips. Place aside.
Lemon curd:
Combine all the ingredients in a heatproof bowl. Place over a hot water bath.
Cook the curd for about 20 minutes until it reaches 85C and it's thick and creamy.
Remove from heat and pass it through a fine sieve. Cover with plastic wrap on its surface and allow to cool down overnight in the fridge.
Chocolate mousse:
Bloom the gelatin in cold water for 10 minute.
Bring the cream to the boiling point over low heat - don't boil it, it just has to be hot.
Remove from heat and stir in the chocolate. Mix until melted and smooth then stir in the gelatin.
Allow the chocolate to cool down slightly then add the vanilla, rum and a pinch of salt.
Fold in the whipped cream then spoon the mousse into your prepared cake rings, filling them with only a thin layer of mousse. Place in the freezer for 10 minutes then spoon a thin layer of lemon curd on top. Cover with the remaining chocolate mousse, splitting it equally between the cake rings.
Place in the freezer for 2-3 hours until well set.
Swiss meringue:
Combine the ingredients in a heatproof bowl and place over a hot water bath. Keep on heat for a few minutes, mixing constantly with a whisk until the mixture is hot and the sugar has dissolved - a thermometer should read around 65C.
Remove from heat and begin mixing with an electric mixer until the bowl feels cold to the touch. It will take up to 7-8 minutes.
Remove the cakes from the freezer and carefully unmold them.
Cover each cake with whipped meringue then torch it with a blowtorch. - it is best to do this just before serving.