Butter six 175ml metal dariole moulds and line each base with a small disc of baking paper. Break the chocolate into pieces and put in a heatproof basin with the butter. Place over a pan of gently simmering water until melted, stirring occasionally. Remove from the heat and leave to cool for 10 minutes.
Use an electric whisk to whisk the whole eggs, egg yolks, lime zest and caster sugar together until pale and thick. Gently fold in the melted chocolate and butter. Sift the flour over the chocolate mixture and fold in lightly. Spoon into the prepared moulds and place in the fridge for at least 30 minutes (and up to 8 hours) before cooking.
Preheat the oven to 180°C fan/200°C/Gas 6. Remove the puddings from the fridge 15 minutes before serving. Bake for 10–11 minutes until well risen but still wobbly in the middle. (Add a minute to the cooking time for each hour that the puddings are chilled, up to 3 minutes extra.)
Remove from the oven and loosen the side of each pudding with a roundbladed knife. Turn out on to six dessert plates and remove the lining paper. Dust the puddings with icing sugar and serve with crème fraîche.