Peel sweet potato and the potatoes. Cut them into chunks and boil until just tender. Drain well and mash.
Chop the red pepper and add to the mashed potato with the chillies and coriander, seasoning well. Stir in about half the breadcrumbs, carrot and the seeds to make a soft dough. Mix well and then shape into 10 burgers.
Lightly whizz the remaining breadcrumbs in a food processor to make finer crumbs (but not a powder). Then coat each burger.
Heat the oil in a frying pan. Fry the burgers 2-3 at a time, for 2-3 minutes on each side, until golden.
Serve in burger buns with lettuce and relish, and cherry tomatoes if desired.
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