Allow the butter to come to room temperature. Brush the ramekins upwards with the butter and then coat with the caster sugar. Tip out any excess sugar.
Preheat the oven to 190'C.
Lightly beat the sugar, egg yolk and the whole egg with a tablespoon of the milk. Add the flour and stir well, making sure the mix is free of lumps. Bring the remaining milk and cream to the boil, pour over the egg mix and combine. Return to the heat and cook until the mixture is thick and the flour is cooked.
Remove from the heat and whisk in the butter, rum and the dark chocolate.
Place the mixture in a bowl and allow to cool.
Whisk the egg whites until they start to develop peaks. At this stage add the caster sugar and continue whisking until the meringue becomes glossy and thick.
Place 45grams of the souffle base into a bowl and add a third of the meringue. Mix well using a whisk until there are no lumps. Remove the whisk and replace with a spatula. Gently fold in half of the meringue mix. Once the mixture is a uniform colour, add the remaining meringue and mix well.
Fill the ramekins with the meringue mix and smooth over using a pallet knife. Bang the ramekins on the surface to remove any large air bubbles.
Bake in the oven for 10-12 minutes.
Sprinkle the souffle with icing sugar and serve immediately
«Always use eggs which are 3 or 4 days old for souffles. This will enable the souffle to rise more.»