In a microwave-safe bowl, combine unsalted butter and semi-sweet chocolate. Heat in the microwave on medium power, stirring every 30 seconds until the mixture is completely smooth and glossy, about 1–2 minutes total.

Using an electric mixer, beat 2 large eggs until frothy and double in volume. Gradually add fine sugar while mixing until it dissolves completely.

Carefully pour the melted chocolate and butter mixture into the beaten eggs and sugar. Gently fold together until thoroughly combined.

Sift in all-purpose flour and baking powder, along with a pinch of salt and vanilla extract. Mix gently until just combined.

Preheat your Air Fryer to 375°F (190°C). Grease four 4oz ramekins with butter.

Pour the batter into the greased ramekins, filling each one about three-quarters full.

Place the filled ramekins in the Air Fryer basket ensuring space between each. Air fry for 7-9 minutes depending on desired gooeyness.

Once cooked, carefully remove ramekins and allow to cool for about 2 minutes before inverting onto a plate.