Add butter and chocolate to a microwave-safe bowl. Microwave on high in 30 seconds increments stirring until the chocolate is fully melted. Set aside.
Beat eggs with an electric beater until frothy. Add sugar and beat till dissolved. Add the melted chocolate and butter mixture to the beaten eggs and stir to combine.
Add the baking powder, vanilla extract, a pinch of salt and all-purpose flour. Stir until well combined.
Preheat Air fryer at 375F. Grease 4 4oz ramekins with butter. Fill the ramekins with the batter until ¾th full. Place the ramekins in the Air fryer basket and bake for 7 minutes for a gooey center and around 9 minutes for a thick center.
Remove the ramekins from the Air fryer. The ramekins will be really hot. Use oven mitts or a folded kitchen/dish towel to lift the ramekins. Allow to cool for 2 minutes.
Now, gently run a knife around the cake to loosen it and invert it onto a plate. Serve immediately with ice cream and berries with chocolate shavings. Or use whipped cream and berries on top.