Preheat your oven to 425°F (220°C).

Grease four 6-ounce ramekins with butter and dust with cocoa powder or flour.

In a heatproof bowl, combine chopped chocolate and butter. Melt over a pot of simmering water or in the microwave in 30-second intervals until smooth.

In another bowl, whisk together eggs, egg yolks, and granulated sugar until slightly thickened and pale.

Gently fold the melted chocolate mixture into the egg mixture.

Sift flour and salt over the batter and fold in until just combined.

Pour batter evenly into prepared ramekins, filling each about 3/4 full.

Place ramekins on a baking sheet and bake for 12–14 minutes.

Let the cakes sit for 1 minute, then run a knife around the edges to loosen.

Invert ramekins onto plates, let sit for 10 seconds, then gently lift.

Dust with powdered sugar and serve warm.