Preheat the oven to 170°C (325°F) or 150°C (300°F) fan-forced. Brush a 2 litre (70 fl oz/8 cup) capacity ovenproof dish (about 20 cm/8 in diameter) with melted butter to grease. Lightly dust with cocoa powder, tapping out any excess.
Place the chocolate and butter in a medium heatproof bowl over a saucepan of simmering water, making sure the base of the bowl doesn’t touch the water, and stir until melted and smooth. Transfer the mixture to a large bowl and stir in the marsala, 110 g (33/4 oz/1/2 cup) of the caster sugar and the egg yolks.
Use an electric mixer with a whisk attachment to whisk the egg whites in a clean, dry large bowl on medium speed until soft peaks form. Add the remaining 55 g (2 oz/¼ cup) caster sugar and whisk until thick and glossy. Add one-third of the egg white mixture to the chocolate mixture and use a large metal spoon or spatula to fold together. Fold through the remaining egg white mixture until just combined.
Pour the mixture into the prepared dish. Bake in the preheated oven for 55–60 minutes, or until crumbs cling to a skewer inserted in the centre.
Remove the pudding from the oven and set aside for 5 minutes. Dust with icing sugar and serve in scoops with cream or ice cream.
This pudding is also delicious served at room temperature. Leave to cool in the dish before serving.
Any leftover pudding will keep covered in the fridge for up to 3 days. Leave to stand at room temperature for at least 30 minutes before serving.
Chocolate Soufflé Cake – Bake the mixture in a 22 cm (81/2 in, base measurement) spring-form cake tin that has been base-lined with baking paper, and then greased and dusted with unsweetened cocoa powder. Bake at the same temperature for 55–60 minutes. Leave the cake to cool in the tin. Cut into wedges to serve.