Heat the oil in a large saute pan over a medium heat. Gently saute the onion and garlic until they begin to soften.
Add the finely chopped green pepper and fry for a further minute or two, until it softens.
Add the toasted and ground coriander and cumin seeds and fry for a further minute.
Stir in the kidney beans, tomato puree and finally the chopped tomatoes.
Pop the lid on, reduce the heat and simmer for 15-20 minutes, stirring occasionally and squashing some of the kidney beans with the back of a wooden spoon. This can be cooled and reheated later at this stage, if needed.
Meanwhile, prepare the tortilla chips.
Mix together the flour, polenta, baking powder, salt and spices in a small bowl.
Add the hot water and vegetable oil, and combine well with a wooden spoon.
Knead for one minute until it forms a smooth ball. Wrap in cling film and chill in the fridge for 10-15 minutes.
Preheat the oven to 170 C/150 C (fan).
Divide the dough into six even pieces and roll out to a thickness of 1 mm, about 20 cm in diameter.
Heat a nonstick pan over a medium high heat and cook the tortilla for 2 minutes on each side, until browned slightly.
While still warm, cut the tortilla into 6 triangle chips and arrange on a baking tray, sprinkling with flakes of sea salt, if desired.
Repeat with the remaining dough.
Bake the tortilla chips for 10-12 minutes and leave to cool completely before eating. They should be lovely and crispy.
When the beans are ready, stir in the chopped leafy greens and cook until they are just wilted. Squeeze in the lemon juice and stir in the fresh coriander leaves.