Preheat the oven to 220°C / 425°F / Gas mark 7.
Line a baking tray with greaseproof paper and place on the top shelf.
Brush 6 x 150ml ramekins with melted butter, sprinkle with the 2 tablespoons of caster sugar, then tip out any excess.
Melt the chocolate and cream in a bowl over a pan of simmering water, then remove from the heat.
Mix in in the egg yolks.
Whisk the egg whites until they hold their shape, then add the sugar, 1 tablespoon at a time, bringing it back to the same consistency.
Mix a spoonful into the chocolate, then gently fold in the rest.
Fill the ramekins quickly, wipe the rims clean.
Turn oven down to 200°C / 400°F / Gas mark 6.
Place the ramekins onto the baking tray, then bake for 8-10 minutes until risen with a slight wobble.
Don’t open the oven door too early as this can cause them to collapse.
Once the soufflés are ready, dust with icing sugar and serve straight away.