Ingredients:
1 stick unsalted butter
7 ounces good quality bittersweet chocolate, between 62% and 70% cocoa
2 whole eggs
2 egg yolks
1/4 cup granulated sugar
Pinch of Kosher salt
2 tablespoons all-purpose (AP) flour

Preheat the oven to 450 degrees F.  Butter and lightly flour four 6-ounce ramekins.  Tap out any excess flour and set the ramekins on a baking sheet.  In a double boiler over simmering water, melt the butter with the chocolate, stirring slowly to combine. 

In a medium bowl, beat the eggs, egg yolks, sugar, and salt at high speed until thickened and pale yellow. Quickly fold the melted chocolate into the egg mixture in addition to the flour. Spoon the batter into the prepared ramekins and bake for 10 to 12 minutes, or until the sides of the cakes are firm but the centers are soft.  Let the cakes cool for about one minute, and then cover each cake with a dessert plate.  Carefully invert each one and let stand for 10 seconds, then unmold.  Serve immediately.