Prepare the Ramekins:

1. Butter and dust: Generously butter the inside of four 6-ounce ramekins using a pastry brush, making sure to coat every surface including the rim. This step is crucial for easy unmolding. Dust the buttered ramekins with cocoa powder, tapping out any excess. Place the prepared ramekins on a baking sheet and set aside.
2. Preheat oven: Position a rack in the center of your oven and preheat to 425°F (220°C). The high temperature is essential for creating that molten center, so make sure your oven is fully preheated before baking.

Make the Batter:

3. Melt chocolate and butter: Place the chopped chocolate and butter in a microwave-safe bowl. Microwave in 30-second intervals, stirring between each interval, until completely melted and smooth (about 1-2 minutes total). Alternatively, you can melt them together in a double boiler over simmering water. Let the mixture cool for 2-3 minutes while you prepare the eggs.
4. Beat eggs and sugar: In a large mixing bowl, combine the whole eggs, egg yolks, and sugar. Using a whisk or electric mixer, beat vigorously for about 2-3 minutes until the mixture becomes pale, thick, and slightly fluffy. It should fall in ribbons from the whisk when lifted. This step incorporates air and creates the proper texture.
5. Combine wet ingredients: Pour the slightly cooled chocolate mixture into the egg mixture. Add the vanilla extract and salt. Gently fold together using a rubber spatula until just combined and no streaks remain. Be gentle to preserve the air you whipped into the eggs.
6. Add flour: Sift the flour over the chocolate mixture (this prevents lumps). Gently fold it in with a few swift strokes until just incorporated. The batter should be glossy, smooth, and thick but pourable. Don’t overmix—a few small lumps are fine.

Bake the Cakes:

7. Fill ramekins: Divide the batter evenly among the prepared ramekins, filling each about ¾ full. The batter should come to about ½ inch from the rim. Gently tap each ramekin on the counter to release any air bubbles.
8. Bake: Place the baking sheet with ramekins in the preheated oven. Bake for 12-14 minutes. The cakes are done when the edges are set and puffed up, but the centers still look slightly soft and jiggly when you gently shake the pan. The tops should have a thin crust but shouldn’t look completely set. For a more molten center, bake for 12 minutes; for a slightly less runny center, go for 14 minutes.
9. Cool briefly: Remove from the oven and let the cakes rest in their ramekins for 1 minute. This brief rest helps them set just enough to unmold without falling apart.

Serve:

10. Unmold: Run a small offset spatula or butter knife around the edge of each cake to loosen it. Place a dessert plate upside down over each ramekin. Using oven mitts (the ramekins will still be hot), quickly flip both the plate and ramekin together. Gently lift the ramekin off—the cake should slide out perfectly. If it sticks, give the ramekin a gentle tap.
11. Garnish and serve immediately: Dust with powdered sugar, add a scoop of vanilla ice cream, garnish with fresh berries and mint if desired, and serve immediately while the center is still warm and flowing. Encourage your guests to cut into the center right away to enjoy that spectacular molten effect!