Steam the leeks for 4 minutes in a colander or steamer over a pan of boiling water. Remove from the heat and leave to cool.
In a large bowl, combine the cooled leeks, feta cheese, eggs and breadcrumbs.
Using a tablespoon of the mixture at a time, mould it into round patties with your hands.
Heat the oil in a shallow heavy frying pan over a high heat. Shallow-fry the paties for about 5 minutes on each side or until golden brown, cooking in batches if necessary. Drain on kitchen paper, and serve warm.