Heat the oil until it's smoking hot. Allow to cool completely.
In a large bowl, mix together the carrots and raw mango batons.
Cut the stalks off the chillies. Slit the chillies lengthways down the centre but don't cut all the way through. If your chillies are large or thick, cut them into smaller pieces and then split lengthways. You can wear gloves if you like.
Mix together the mustard seeds, turmeric, asafoetida, salt and citric acid.
Fill the split chillies with the dry mustard seed masala. I use gloves so my nails don't stain.
Add any leftover mustard seed masala, along with the filled chillies to the cut carrots and mango.
Pour the cooled oil into the pickle. Use your hands to toss everything well.
Pile the Athela Marcha (Instant Chilli Pickle) into a clean, sterilised jar. Cover with a tight-fitting lid. Refrigerate and enjoy within 3 weeks.