In a small bowl, whisk together egg yolks, erythritol, salt and vanilla.

Set aside.

In a medium saucepan, heat cream over medium-low heat for 4 minutes to a low simmer.

Whisk a spoonful of thickened cream into egg mixture to temper eggs, then slowly whisk egg mixture into saucepan with remaining heavy cream.

Add chocolate chips and cinnamon and continually stir for 10 minutes on simmer until chocolate is melted.

Remove pan from heat and evenly distribute chocolate mixture among four ungreased custard ramekins.

Preheat air fryer at 180°C for 3 minutes.

Place two ramekins in air fryer basket.

Cook for 7 minutes.

Transfer ramekins to a cooling rack.

Repeat cooking with remaining two ramekins.

Allow ramekins to cool for 15 minutes, then refrigerate covered for at least 2 hours before serving.