Place all in slow cooker on high for 3 hours, then turn to low for 3 hours, give it a good stir when the mood strikes you, if you're like me that's around every 45 mins - when you take the lid off, tip the condensation into the sink.
Continue to cook until good colour is achieved and chutney is thick. Bottle while still hot, preferably into warm, steralised jars.
Note: For those asking how much 15 mangoes would be…weigh your prepared apples, and then times by 3, you need a 3 to one ratio, mangoes to apples.