Preheat oven to 425°F. Using 1 tablespoon of butter, grease six 6.5oz ramekins. Lightly cover the buttered ramekins with cocoa powder. Tap out excess. Set the ramekins on a baking sheet.
In a double boiler, over simmering water, melt butter and chocolate. Remove from heat and set aside.
In a large bowl, at medium-high speed, beat eggs, egg yolks, sugar, and salt until light and thickened.
Fold the chocolate mixture and flour into the egg mixture. Evenly distribute the batter into the prepared ramekins.
Bake for 9-10 minutes or until the sides of the cakes form a crust but the center is still soft. Remove from the oven and allow the cakes to rest for 1 minute. Carefully invert each cake into a plate and unmold.
Sprinkle with powder sugar and garnish with fresh raspberries. Serve immediately.