Fry the onion in 3 tablespoons of oil over a medium heat until it is soft and lightly coloured. Add the courgettes, and sauté, stirring, until they too are soft.
In a bowl, beat the eggs with the flour until well blended. Add black pepper (there is no need for salt because the feta cheese is very salty) and the herbs, and mix well. Fold the mashed feta into the eggs, together with the cooked onions and courgettes.
Film the bottom of a preferably non-stick frying pan with oil and pour in the mixture by the half-ladle (or 2 tablespoons) to make a few fritters at a time. Turn each over once, and cook until both sides are browned a little. Drain on kitchen paper.