Use 5g of butter to melt to brush 2 moulds, then completely cover the buttered moulds with cocoa powder.
In a bowl, whisk the butter and sugar until it turns creamy. Add the egg continuing to whisk then fold in the flour. Pour in the melted chocolate until you have a smooth batter.
Preheat the oven to 200°C fan.
Divide the mixture between the two moulds and chill for 20 minutes then bake for 10 minutes.
Remove from the oven and leave to stand for 1 minute. Carefully tip out onto a plate and serve with Madagascan vanilla ice cream.