Heat oven to 425 F/218 C.
Break up chocolate into pieces. Place chocolate and butter in a bowl. Heat water in a small pot until simmering and set bowl on top. Bottom of bowl should not touch water. Stir butter and chocolate occasionally and melt until smooth. Remove from pot, set on a towel and place on counter.
Generously butter and sugar 4 ramekins or any 4 oven proof containers. Place ramekins on a sheet tray.
Place eggs and yolks in a large bowl and whisk well. Add sugar and whisk for 1 minute. Scrape down sides of bowl and whisk well. Add salt and mix. Add flour and whisk to combine. Mix in vanilla extract. Add chocolate while whisking. Make a smooth batter.
Using an ice cream scoop, divide batter evenly into ramekins. Bake in the heated oven for 10-12 minutes until edges are set and middle looks set but jiggly.
Remove from oven and let stand for 1 minute. Using tongs, place a ramekin on a cloth and cover with a small plate. Turn over onto plate and leave on your counter for 1 minute. Lift up ramekin to dislodge cake. Tap on bottom and sides of ramekin if cake is difficult to turn out. If desired, serve with vanilla ice cream and berries.
***Substitute cocoa powder or all purpose flour for sugar to coat ramekins.