Slice leeks fairly finely. Cut the cheese into slice about 8mm thick then cut each slice in half to make squarish pieces.
Heat the oil in a frying pan, put in the cheese and fry for 1-2 minutes until golden brown on one side, then flip the pieces over and fry the other side.
Drain the cheese on kitchen paper and leave on one side.
Put the leeks in the frying pan and stir-fry for about 5 minutes or until they are just tender. Then add the cumin seeds and stir for a moment or two longer. Add the lime juice and season with salt and pepper.
Put the cheese back into the pan with the leeks and heat through for a few minutes.