Put the shallots, halloumi and sweet potato in a mixing bowl with the chilli, mint, lime zest and juice and tablespoon of olive oil.
Mash the avocado with the cream, vinegar, coriander and lime and season.
Heat a barbecue or griddle pan, then cook the sweet potato and shallots for 5 minutes on each side or until charred and tender. Cook the halloumi for 1 minute on each side or until charred.
Halve and toast the burger buns.
Spread the mashed avocado onto the toasted bun bases, add a couple of little gem leaves then top with the shallots, halloumi and sweet potato. Pop the top of the bun on and serve with tomato chilli jam.