01 - Preheat the oven to 400°F. Generously butter two 8-ounce ramekins and dust with granulated sugar, tapping out the excess.
02 - Set a heatproof bowl over a saucepan of simmering water. Melt the chocolate, 1 tbsp butter, and heavy cream together, stirring until smooth. Remove from heat and let cool slightly.
03 - In a small bowl, whisk the egg yolks with vanilla extract until thick. Stir into the cooled chocolate mixture.
04 - In a clean bowl, beat the egg whites with a pinch of salt until soft peaks form. Gradually add 2 tbsp sugar while beating, until stiff, glossy peaks form.
05 - Gently fold one-third of the egg whites into the chocolate mixture to lighten it. Then carefully fold in the remaining egg whites until just combined.
06 - Divide the mixture evenly between the prepared ramekins. Run your thumb around the inside edge of each ramekin to help the soufflés rise evenly.
07 - Bake on a baking tray in the center of the oven for 12-15 minutes, until the soufflés have risen and the tops are set but still slightly wobbly in the center.
08 - Serve immediately, dusted with powdered sugar or accompanied by whipped cream if desired.