Place butter, brown sugar, white sugar and cocoa powder in a microwave safe bowl. Microwave in 20 second batches, stirring well after each time, until butter is melted and well combined.
MIX IN VANILLA & EGG
Add vanilla and stir to mix through. Set bowl aside for a minute to allow to cool slightly. Add egg and mix well.
Add flour and mix well to combine.
FOLD IN CHOCOLATE
Fold chocolate chips into the batter. I like to also chop my favourite chocolate bar into chunks and fold that through too for extra choocolate-y goodness!
DIVIDE INTO MINI LOAF PANS
Evenly divide the mixture across the prepared mini loaf pans (or just pour into 1 regular sized loaf pan if that's what you have on hand.
TIME TO BAKE
Bake in the air fryer on 160C / 320F for 20-25 minutes or until a toothpick inserted comes out with only a few fudgy crumbs attached. Leave in the loaf pans for 10 minutes to cool, then transfer to a wire rack to cool completely.