Process the onions and garlic together in a food processor in batches. Cook until almost dry. Grate the tomatoes and peppers. Mix together the yoghurt, grated vegetables and the cooked onion and garlic. Chop the parsley, dill and mint and add to the mixture. Make a pile of flour, scooping out a well in the middle, and add the mixture. Mix the flour into the vegetables as if making bread dough, slowly incorporating the flour. Let rest in a corner. Knead the mixture each evening. When you begin to notice a fermented smell, break the mixture into small pieces and spread them on a large cloth like a bedsheet or tablecloth. When the pieces start to dry, crumble them between your palms and then force them through a sieve to make tiny pieces. Lay these out again on a sheet or cloth until completely dry.