Brush four 6-oz ramekins generously with softened butter. Dust with cocoa powder and tap out any excess. Place the ramekins on a small baking sheet and put them in the freezer while you make the batter.

Combine the chopped bittersweet chocolate and butter in a heatproof bowl. Melt together over a double boiler or in the microwave in 30-second intervals, stirring between each interval, until completely smooth. Let cool slightly.

Whisk the eggs, egg yolks, and granulated sugar together in a medium bowl until pale and slightly thickened, about 1–2 minutes.

Pour the melted chocolate mixture into the egg mixture and whisk until fully combined. Add the flour and pinch of salt and fold in gently until just incorporated — do not overmix.

Remove the ramekins from the freezer and divide the batter evenly among all four. They should be about three-quarters full.

Place the filled ramekins back in the freezer for 30 minutes. This step is critical — the cold center is what creates the molten middle when baked.

While the ramekins are freezing, preheat your oven to 425°F (220°C).

Bake the ramekins directly from the freezer for exactly 12 minutes. The edges should be fully set and the center should jiggle when you gently shake the pan. Do not overbake.

Remove from the oven and let the ramekins rest for 1 minute. Run a knife around the edge of each ramekin, then place a plate on top and carefully flip to unmold. Serve immediately with vanilla ice cream or a dusting of powdered sugar.