Heat the oil in a large non-stick pan then add the onion and cook gently without colouring until soft. Meanwhile, beat the eggs lightly and season with sea salt and black pepper.

Add the potato cubes to the onion and cook gently until warmed through, then add the greens, parsley and flaked fish. Combine well and season.

Maintain a low heat and add the eggs to the pan. Leave the eggs to cook without interfering, giving the pan a little shake after six or seven minutes. You should see the bottom of the frittata is set but the top remains wet.

Sprinkle the cheese on top and place the pan under a moderate grill for around 10 minutes, as you want to ensure the frittata cooks slowly until set and golden.

Leave the frittata to cool in the pan for around 10 minutes. Either cut it into portions in the pan or carefully remove it on to a plate.

Serve on warmed plates with a simple salad tossed in vinaigrette or some toasted and buttered sourdough.