Line an 18cm baking pan with baking paper. Set aside.
Make the icing by adding all the ingredients except the chocolate into the inner pot and select Saute on low.
Bring to a boil until everything is dissolved, stirring frequently then press cancel and add the finely chopped chocolate.
Remove the inner pot and give it a shake to submerge all the chocolate, then leave for a minute to allow the chocolate to melt. Then whisk the icing together and tansfer to another bowl to cool and give the inner pot a clean.
In another bowl, combine the flour, bicarbonate of soda, salt, instant espresso powder and cocoa and whisk with a fork until combined.
Mix together the sugar, hot water, coconut oil and vinegar until the coconut oil has melted, then stir into the dry ingredients.
Pour the cake mix into the prepared tin, then place the tin into the air fryer basket. Put the basket into the inner pot and secure the air fryer lid.
Select Bake and set the temperature to 158°C and time to 44 minutes.
Cook until a skewer inserted into the cake comes out clean
Once the cake is baked, transfer the tin to a wire rack and let the cake cool in its tin.
When the cake is cool, top with the cooled prepared icing and sprinkle chopped pistachios on top.