Preheat oven to 180°C and grease a 20cm round cake tin with butter.
Melt 15g of butter over gentle heat and set aside.
Beat sugar and eggs with an electric mixer over simmering water until pale and frothy.
Remove from heat and continue beating for two minutes while cooling.
Fold in vanilla, salt, sifted flour, cocoa powder, and melted butter.
Bake for 10–12 minutes until the centre is firm.
Drizzle with 2 teaspoons of whisky and cool completely in the tin.
Boil golden syrup and sugar together for 5–10 minutes until golden caramel.
Stir in cardamom and bicarbonate of soda, then pour into a lined 20cm square tin.
Let honeycomb set for one hour before breaking into chunks.
Boil 200ml water with sugar and cardamom, then pour through a strainer over chopped chocolate.
Stir until smooth, add 1 tablespoon of whisky, and fold in whipped cream.
Spoon chocolate mixture over the sponge and chill for several hours or overnight.
Remove from tin and decorate with honeycomb and gold dust before serving.