Prep the ramekins: Heat your oven to 425°F (220°C). Generously butter the inside of 4 to 6 ramekins. Dust with cocoa powder, tapping out the excess. This helps the cakes release cleanly.

Melt chocolate and butter: In a heatproof bowl, combine the chocolate and butter. Melt over a saucepan of barely simmering water (double-boiler style), stirring until smooth. Or microwave in 20–30 second bursts, stirring between each, until glossy.

Whisk eggs and sugar: In a separate bowl, whisk the eggs, egg yolks, sugar, and salt until slightly thick and lighter in color, about 1–2 minutes by hand. You want a bit of volume for a tender crumb.

Combine mixtures: Slowly pour the warm chocolate mixture into the egg mixture while whisking. Add vanilla. Whisk just until smooth and uniform.

Fold in flour: Sift the flour over the batter. Gently fold with a spatula until no dry spots remain. Do not overmix—this can toughen the cake.

Fill the ramekins: Divide the batter evenly among the prepared ramekins. Place them on a baking sheet for easy handling.

Bake: Bake for 10–12 minutes (8–10 minutes for smaller ramekins or muffin tin). The edges should look set and firm, while the centers still look soft and slightly jiggly. A cracked top is normal.

Rest and unmold: Let the cakes rest for 1 minute. Run a thin knife around the edge to loosen. Invert each onto a dessert plate. Lift the ramekin carefully—steam will be hot.

Serve immediately: Dust with powdered sugar, add a scoop of vanilla ice cream, and garnish with berries if you like. The center should flow when cut.