1. For the coriander mayo, place the coriander and vegan mayo in a blender and blitz until smooth. Season to taste.
2. Heat the oil to 175°C.
3. Drop the onion bhajis into the hot oil and fry until crispy, about 2-3 minutes.
4. Remove and drain the bhajis on kitchen paper.
5. To assemble the burgers, spread coriander mayo on the bottom, then lettuce, then bhaji.
6. Finish with fresh coriander, sliced red onions, mango sauce then the top of the bun.