Place the butter in the small saucepan and heat until melted.
Generously brush the melted butter onto the insides of the pudding moulds.
Place the moulds in the freezer for 10 minutes.
Remove from the freezer and brush more melted butter over the chilled butter (which will immediately chill once it touches the frozen butter). Try to ensure that there is an even layer of butter with no streaks.
Dust the inside of the moulds with cocoa powder which should completely coat the butter. Return to the freezer until needed.
Quarter fill the saucepan with water and bring to the boil. Reduce the heat to a simmer and place a bowl over the top. Add the chopped chocolate and pieces of cold butter and continue to heat, stirring all the while, until melted.
Remove the bowl from the heat and stir until smooth. Leave to cool for about 10 minutes.
Place the eggs, egg yolks and caster sugar in a mixing bowl and beat with the electric hand whisk until thick, voluminous and pale in colour.
Sift the flour into the egg and sugar mixture and fold in evenly.
Pour the melted chocolate into the mixture in thirds, beating well between each addition, until all the chocolate is added, and the mixture is completely combined to a loose cake batter.
Transfer the fondant batter into the jug, then evenly divide between the moulds. (If you wish the fondants can now be frozen for up to a month and cooked from frozen. If cooking from frozen just add 5 minutes to the usual cooking time).
Place the fondants in the fridge for 20 minutes.
Preheat the oven to 200C/400F/gas 6.
Place the fondants on the baking sheet and bake in the preheated oven for 10-12 minutes until the tops have formed a crust and they are starting to come away from the sides of their moulds.
Remove from the oven, then leave for a minute before turning out.
Loosen the fondants with a knife by moving the tops very gently so they come away from the sides, easing them out of the moulds.
Tip each fondant lightly onto your hand so you know it has come away, then sit it in the middle of each serving plate.
Serve with a quenelle of vanilla ice-cream and/or a dollop of whipped cream.
