01 - Preheat oven to 400°F. Generously butter two 8-ounce ramekins and dust with granulated sugar, tapping out excess.
02 - Set heatproof bowl over saucepan of simmering water. Melt chocolate, 1 tablespoon butter, and heavy cream together, stirring until smooth. Remove from heat and cool slightly.
03 - Whisk egg yolks with vanilla extract in small bowl until thick. Stir into cooled chocolate mixture.
04 - Beat egg whites with 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 egg whites into chocolate mixture to lighten. Carefully fold in remaining egg whites until just combined.
06 - Divide mixture evenly between prepared ramekins. Run thumb around inside edge of each ramekin to help soufflés rise evenly.
07 - Bake on baking tray in center of oven for 12-15 minutes until risen and tops are set but still slightly wobbly in center.
08 - Serve immediately, dusted with powdered sugar or accompanied by whipped cream if desired.