Preheat your oven to 425°F (220°C) to ensure perfect baking.
Generously butter your ramekins and dust them lightly with flour, shaking off any excess.
In a mixing bowl, combine chopped semi-sweet chocolate and the stick of butter. Microwave in 30-second intervals, stirring in between until melted and smooth.
In another bowl, whisk together the eggs, egg yolks, and sugar until light and fluffy.
Slowly pour the melted chocolate and butter mixture into the egg mixture, stirring constantly to combine.
Gently fold in the flour until just combined, being careful not to overmix.
Divide the batter evenly among the prepared ramekins, filling about 2/3 full.
Place ramekins on a baking sheet and bake for 12-14 minutes, until edges are firm but centers remain soft.
Remove from oven and let rest for 1 minute to set the edges.
Run a knife around the edges, invert onto a plate, and serve immediately to enjoy the gooey center.