Grease six 175ml dariole moulds with butter and line the bases with baking parchment.
Coat the moulds with a sifted mix of cocoa powder and plain flour and shake out the excess.
Melt the chocolate and butter in a heatproof bowl set over a pan of simmering water.
Cool the chocolate mixture for 10 minutes.
Whisk eggs, egg yolks, sugar, and lime zest until pale and thick.
Fold the melted chocolate mixture into the egg mixture until just combined.
Sift in the self-raising flour and fold in carefully.
Pour mixture into moulds, cover with film, and chill for at least 30 minutes.
Simmer lime marmalade and lime juice in a saucepan for 4 minutes until reduced.
Cool the lime syrup completely at room temperature.
Heat coconut milk and double cream until just simmering.
Whisk egg yolks and cornflour in a bowl until smooth.
Pour the warm liquid over the yolks, return to the pan, and stir over heat until thickened.
Preheat the oven to 200°C and bring fondants to room temperature.
Bake the fondants on a tray for 11 minutes until slightly wobbly in the centre.
Turn out fondants onto plates with coconut custard, lime syrup, and a dollop of cream.