Preheat your oven to 425°F (220°C) and butter and flour five ramekins or a muffin tin.

Melt the butter and chopped chocolate together in a microwave or a double boiler, then stir until smooth.

In a separate bowl, whisk together the eggs, egg yolks, and sugar until light and fluffy.

Gradually fold the melted chocolate mixture into the egg mixture, then gently mix in the flour, vanilla extract, and salt until just combined.

Divide the batter evenly among the prepared ramekins and bake for 10-12 minutes, or until the edges are set but the center remains gooey.

Carefully invert the cakes onto serving plates and serve immediately, optionally with a dusting of powdered sugar or a scoop of ice cream.