Grease 3 6-ounce ramekins with butter or cooking spray and set them aside.
Add butter and chocolate to a microwave-safe bowl, and microwave for about 1 minute until melted, stirring every 30 seconds. Set aside.
In a separate large bowl, using an electric mixer, beat egg, egg yolk, vanilla extract, and sugar, until well combined, about 2 minutes.
Then add the flour, the chocolate mixture, and a pinch of salt. Use a spatula to stir until fully combined, do not overmix.
Pour the mixture into the prepared ramekins, filling each one a bit more than halfway.
Preheat the air fryer to 370 degrees F.
Arrange the ramekins in the air fryer basket and air fry for 8-10 minutes. The sides should be settled and the center still a bit soft.
Once done, use oven mittens to carefully remove the ramekins from the air fryer basket.
Allow the cakes to cool for about 1 minute. After that, use a butter knife to loosen the cake from the ramekin, cover with a plate and flip it. Gently tap to loosen the cake.
Serve with fresh whipped cream, fresh berries, topped with ice cream, or with powdered sugar.
The described above is chocolate lava cake, for the other varieties follow the same recipe exactly to make the chocolate cake batter.
After that, choose one of the fillings, prepare it, and set it aside.
Fill the ramekin a bit less than halfway with chocolate batter, add 1 tablespoon of the chosen filling, and top with more batter, so the ramekin is filled a bit more than halfway.
Cook per recipe instructions.