Grease 3 (6-ounce) ramekins with cooking spray.
Place butter and chocolate in a small microwave-safe glass bowl. Microwave on high for 1 minute, stirring every 30 seconds until melted.
Beat egg, egg yolk, sugar and vanilla in a separate medium bowl until light and fluffy.
Add flour, salt and chocolate mixture to egg mixture and fold together until combined.
Pour batter into prepared ramekins, filling halfway.
Place ramekins into the air fryer.
Set temperature to 375°F/190°C and time to 7 to 9 minutes, then press Start/Stop to cook until top is just set but cake slightly jiggles.
Run knife around edge of cake and invert onto serving plate.
Serve cake with raspberries and ice cream.
Tip: Garnish with powdered sugar to create an extra-sweet treat!