Creating Moelleux au Chocolat is straightforward if you follow these simple steps:

1. Preheat Oven: Preheat your oven to 200°C (390°F). Grease four ramekins with butter and dust with flour.
2. Melt Chocolate and Butter: In a heatproof bowl, combine the dark chocolate and unsalted butter. Melt them together over a pot of simmering water or in the microwave, stirring until smooth.
3. Whisk Eggs and Sugar: In a separate bowl, whisk the eggs and granulated sugar together until the mixture is pale and frothy.
4. Combine Mixtures: Pour the melted chocolate mixture into the egg mixture. Stir gently to combine.
5. Add Flour and Salt: Sift the all-purpose flour and add it to the chocolate mixture, along with a pinch of salt. Fold everything together until just combined.
6. Add Vanilla Extract: If using, stir in the vanilla extract for an extra layer of flavor.
7. Pour Batter into Ramekins: Divide the batter evenly among the prepared ramekins.
8. Bake: Place the ramekins in the preheated oven and bake for 10-12 minutes. The edges should be set, while the center remains soft.
9. Cool Slightly: Remove from the oven and let the ramekins cool for about 5 minutes.
10. Serve: Carefully invert each ramekin onto a plate to release the Moelleux au Chocolat. Serve warm.

These steps will guide you in creating this incredible cake effortlessly.