Preheat your oven to 425°F (220°C).

In a heatproof bowl, combine the dark chocolate and unsalted butter over a pot of simmering water. Stir continuously until melted and smooth (5-7 minutes).

In a mixing bowl, whisk together the sugar and large eggs until pale and fluffy (2-3 minutes).

Fold the melted chocolate mixture into the egg mixture gently. Add the vanilla extract and mix well.

Sift the all-purpose flour over the chocolate mixture and fold until just combined.

Grease four ramekins and fill each about three-quarters full with the batter. Place them on a baking sheet.

Bake for 12-14 minutes until edges are firm but centers are wobbly.

Let them cool for 1-2 minutes before inverting onto plates.

Serve warm with a scoop of vanilla bean ice cream or whipped cream.