Brush melted butter on the inside of the ramekins. Place in the freezer for 10 to 15 minutes. Brush with more melted butter and then sprinkle the cocoa powder inside the ramekins. Shake to completely coat the ramekins, and then tap out excess.
Use a double boiler (with water in the bottom pot) or a heatproof bowl over a bowl of simmering water to gently melt the chocolate and butter. Remove from heat and let cool for 10 minutes.
In a large bowl, use an electric hand mixer to beat together the eggs, egg yolks, and sugar until so thick that a spoon dragged across the top of the mixture leaves a trail.
Sift the flour into the egg mixture and then beat until incorporated. Pour the melted chocolate mixture into the egg mixture one-third at a time, beating well between additions until completely combined.
Evenly divide the mixture across the prepared ramekins. Chill them for 20 minutes.
Preheat oven to 400°F while the cakes are chilling.
Place ramekins on a baking sheet and cook for 13 minutes, or until the tops are solid and just starting to pull away from the sides. Remove from the oven and let rest in the ramekins for 3 to 5 minutes.
Use a thin sharp knife to loosen the sides of the cake from the sides of the ramekins. Invert the cakes onto serving plates and gently remove them from the ramekins.
Sprinkle with confectioner's sugar and garnish with fresh fruit, if desired. Serve at once.
