Remove the skin and pith from four of the oranges, slice across thinly and remove the pips. Arrange on a serving plate then sprinkle over the onion and parsley. Season with sea salt and freshly ground black pepper. Dress the salad with a couple of squeezes of the remaining orange, then stick a small sharp knife into the cheese and twist to make little chunks. Scatter these over the top of the salad and serve straight away.