In a small saucepan combine chocolate and butter over medium-low heat. Cook until melted, whisking constantly. Remove from heat and set aside to cool.

In a medium bowl combine sugar, cornstarch and salt. In a separate bowl whisk together eggs, yolks and vanilla.

Add egg mixture to sugar mixture whisking to combine.

Stir chocolate mixture into egg mixture. Refrigerate mixture 2 hours.

Preheat oven to 350 degrees F. Spray 4 (6 ounce) ramekins with nonstick cooking spray, dust with sugar. Spoon approximately 1/2 cup batter into each ramekin.

Bake for 30 minutes. Remove from the oven and let cool for 5 minutes before dusting with confectioners' sugar.

Serve immediately.