Place a sheet pan in the middle of the oven for at least 15 minutes at 350 degrees F.
Combine the butter and chocolate in a mixing bowl on top of a pot of simmering water. If you don't have experience melting chocolate then be very careful not to burn the mixture. Never melt chocolate directly over the cooking element. Heat the chocolate mixture until melted and set aside to cool slightly.
In a mixer on medium-high speed, beat the eggs, the egg yolks and the sugar for about 5 minutes, or until they are thick and a light yellow color. On low speed gradually add the flour and then the chocolate-butter mixture.
Butter 6 (6 to 8-ounce) ramekins and dust with the cocoa powder. Tap out the excess but make sure they are well coated. Pour the batter into the ramekins, filling them about 7/8 of the way to the top. Place on the preheated sheet tray and bake for 15 to 18 minutes. The consistency when done should be where the edges of the cake are firm and the top is still soft to the touch. This dessert has very thin line between being under and overdone!
Remove from the oven and let sit on a cool surface for 3 to 5 minutes. Run a paring knife between the cake and ramekin to loosen the sides. Invert your dessert plate over the ramekin (be careful, they're hot) and flip over. Tap the plate lightly and lift off the ramekin. Serve with vanilla ice cream and garnish with raspberries and strawberries, if desired.
If the cake runs all over the plate you need to increase the cooking time. If the cake is hard and does not ooze chocolate, lessen the cooking time. If the cake does not come out then make sure the ramekins are well buttered and covered in the cocoa.