Chocolate cake for John's birthday

150g caster sugar
275 g plain chocolate, chopped
175 g unsalted butter
10 ml vanilla
5 eggs
40 g (1/4 cup) plain flour
Pinch of salt
Icing sugar for dusting

Preheat oven, 170 degC
Butter springform pan.
Set aside 45 ml of sugar.
Place chocolate, butter and remaining sugar in a pan and cook over low heat until the chocolate and butter have melted and the sugar has dissolved. Remove the pan from heat, stir in the vanilla and leave the mix to cool slightly.
Beat the egg yolks into chocolate mix.
Stir in flour.
Beat the eggs whites slowly, add speed and mix in salt until soft peaks. Sprinkle rest of sugar and beat until whites are glossy and stiff. Beat 1/3 of this into chocolate mix, and then fold the rest softly in.
Pour mix into pan – minimize air bubbles.
Bake for 35-45 min, cool on wire rack, dust with icing sugar.