Preheat the oven to 190°C (375°F). Place 4 ramekins on a baking tray.

Finely chop 75 g dark chocolate.

Bring a small amount of water to a gentle simmer in the saucepan. Set a heatproof mixing bowl over the saucepan without letting it touch the water.

Whisk 40 g caster sugar, 2 egg yolks, 1 teaspoon vanilla extract, 15 g all-purpose flour, and 15 g cocoa powder in the bowl over the double boiler.

Stir 55 ml milk into the cocoa mixture. Remove the bowl from the heat.

Add the chopped 75 g dark chocolate to the warm cocoa mixture. Stir until the chocolate has melted and the custard is smooth.

Whisk 100 g egg whites in a clean mixing bowl until foamy. Gradually add 20 g caster sugar while whisking.

Continue whisking the egg whites until stiff peaks form. Ensure the meringue is glossy and holds its shape.

Fold one-third of the meringue into the chocolate custard to loosen it. Gently fold in the remaining meringue until no white streaks remain.

Divide the soufflé batter evenly among the 4 ramekins. Smooth the tops with a spatula.

Bake the ramekins at 190°C (375°F) for 15 to 18 minutes. Do not open the oven during the first 15 minutes.

Check that the soufflés have risen and a skewer inserted in the centre comes out clean. Serve immediately while puffed and warm.