Put the spring onions, garlic and coriander leaves in a food processor. Pulse until you get a coarse paste. Add the beans and pulse until you get a thick, sticky mixture.
Transfer it to a mixing bowl. Add the spices and seasoning.
Grate the beetroot, using coarse cheese garter. Add this to the beans, together with the lime zest, chipotle paste and the maze flour.
Combine well. You should get a malleable, doughy mixture - you might need to add more polenta or maze flour if it’s too soft.
Divide the mixture into approx. 6 portions and form patties. Put these on a plate, cover and chill until you’re ready to cook them.
Heat a grill, griddle pan or frying pan. Spray the patties with little oil, then cook them until golden.
Alternatively bake them in the oven for about 20 minutes, turning them once.
Serve warm.