Preheat the oven to 410 degrees. Grab 6 ramekins and place them on a baking sheet. Spray each one with non-stick spray. Set aside.
Create double-boiler by filling a medium sauce pan with water. Turn the heat to medium. Once it begins to boil, reduce to medium-low and place a large bowl on top. The bowl should rest on top and NOT touch the water.
Cut butter into tablespoons and place into bowl. Place chocolate on top of butter. They should slowly begin to melt. Stir regularly to combine butter and chocolate together, forming a silky smooth chocolate sauce. Remove from heat when completely melted. Let it cool slightly so it's warm, but not hot.
In a medium bowl, lightly whisk eggs, egg yolk, and vanilla together. Sift powdered sugar into the egg mixture. Add 1/4 cup slightly cooled chocolate to egg mixture and combine. Add remaining chocolate and combine. Do not over mix.
Sift flour into chocolate mixture. Fold flour gently into chocolate mixture with a spatula just until combined.
Grab baking sheet with greased ramekins, Fill each ramekin with the cake mixture about 80% of the way.
Place baking sheet with ramekins into preheated oven and bake for 11-14 minutes. The cake will be done when you see that the perimeter is cooked but the center is still wet. If you have smaller ramekins (less than 6 ounces) you may find that they cook faster than 11 minutes. Just keep an eye on them.
Once they're done, pull them from the oven. Using a heat-proof mitt or pot-holder, grab a ramekin. Use a sharp knife to cut around the edge to release cake from the ramekin. Put a dessert plate on top of the ramekin and gently flip over so that the cake releases from the ramekin and onto the plate. This makes a nice presentation but you can always eat straight from the ramekin.
It tastes amazing without any ice cream or whipped cream. But feel free to serve with either of those if you want. Berries also add a nice touch.