01 - Preheat the oven to 400°F. Generously butter two 8-ounce ramekins and dust with granulated sugar, tapping out the excess.
02 - In a heatproof bowl set over a saucepan of simmering water, melt the chocolate, 1 tablespoon 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 tablespoons 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 to 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.