Heat oven to 375 degrees. Butter and sugar six
6 oz ramekins. Fill a small pot with 1 inch
of water and bring to a simmer. In a metal
bowl large enough to rest on the pot,
combine chocolate and heavy cream. Stir until melted. Remove from heat and
whisk in egg yolks one at a time, being
careful not to scramble. Stir in vanilla.
In a large bowl (or a stand mixer fitted
with whisk attachment) whisk egg whites
on high until soft peaks form. While
whisking, add sugar and salt; whisk on
high until stiff peaks form.
Gently fold chocolate mixture into
whipped egg whites until no streaks
remain. (Do not over-mix or the soufflés
won't rise to the maximum level.)
Carefully spoon mixture evenly among
ramekins. Bake at 375 degrees for 17 minutes,
or until puffed and a cake tester inserted
in the middle comes out clean. Dust
with confectioners' sugar, if desired,
and serve immediately.