Step 1

Line an 18cm round cake tin with several layers of plastic.

Step 2

Place the rice bubbles into a large mixing bowl.

Step 3

Place the golden syrup and butter in a large saucepan over a low heat and heat until the mixture bubbles at the edge, and the butter melts. Remove the pan from the heat and add in the chocolate, and stir gently until everything is melted and combined.

Step 4

Pour the chocolate mix onto the rice bubbles, and stir well to combine. Press the mixture firmly into the lined tin, and then place in the fridge for at least an hour to set.

Step 5

To make the icing, place the egg whites, salt and sugar into a heatproof bowl. Place a medium saucepan over a low heat, with about 3cm of water in the base, and bring it to a simmer.

Step 6

Place the egg white bowl over the saucepan and heat, whisking gently, until the egg white mixture is hot to the touch (about 5 minutes).

Step 7

Remove from the heat and beat, using electric beaters, until the mixture triples in volume and holds a stiff peak.

Step 8

To serve, immediately pile the marshmallow frosting onto the set chocolate crackle cake. If desired, you can torch the frosting with a kitchen blowtorch until it's golden.