Prepare Ramekins:
Spray two 6-ounce ramekins with nonstick cooking spray and set aside.
Melt Chocolate and Butter:
Combine the butter and chocolate in a medium microwave-safe bowl. Melt them together in the microwave for 60-90 seconds, stirring at 30-second intervals until fully melted and combined.
Mix Eggs and Sugar:
In a separate bowl, whisk the egg white, eggs, and granulated sugar until the mixture becomes frothy.
Combine Mixtures:
Carefully pour the egg mixture into the melted chocolate and butter mixture, stirring until well combined.
Add Flour:
Using a spatula, fold in the flour until just combined. Be careful not to overmix.
Fill Ramekins:
Pour the batter evenly into the prepared ramekins.
Air Fry:
Place the ramekins in the air fryer and cook at 370°F (188°C) for 8-10 minutes. Watch closely to ensure they don’t overcook. The cakes are ready when the tops have popped up and the edges are slightly crispy.
Cool and Serve:
Allow the ramekins to cool for a minute. Using a thick dish towel, carefully remove them from the air fryer basket. Run a sharp knife around the edge of the cake to loosen it, then gently flip the cakes onto a serving plate.