Rinse the lentils, cover them with plenty of cold water and leave to soak for 2-3 hours.
Heat a small, heavy-based frying pan over a medium heat. Add the cinnamon, cloves, coriander and cumin seeds and peppercorns, then dry-fry them for 1 minute, or until they release their aromas. Transfer them to a plate to prevent further cooking and leave to cool.
Drain the lentils and put them into a pan with the garlic, ginger and spinach. Cook over a medium heat, stirring, for 1-2 minutes until the spinach begins to release its juice. Reduce the heat, cover and simmer for 10-12 minutes, stirring occasionally, until the liquid has been absorbed – take the lid off towards the end, if necessary, to allow it to evaporate.
Meanwhile, grind the roasted spices finely in a spice mill or with a pestle and mortar, then transfer them to a food processor. Add the lentil and spinach mixture, fresh coriander, mint, chilli, egg, and salt to taste and process. When the mixture is well blended, add the onion and pulse for a few seconds to chop the onion finely rather than puréeing it.
Heat the grill to high and divide the mixture into 16 equal balls. Shape them into round, flat patties about 5 cm (2 in) in diameter.
Line the grill pan with foil and brush lightly with some of the oil. Place the patties on top, brush them with half of the remaining oil and grill for 4 minutes. Turn them over, brush with the rest of the oil and grill for a further 3-4 minutes until brown and crisp. Serve two patties on a grilled pitta bread, garnished with a sprig of mint.
Yellow split peas can be used instead of the lentils. The patties also taste good served with a spoonful of raita.