Trim the roots and any ragged greens off the spring onions. Finely slice them, white and green parts. Finely grate the zest off the lemon. Finely chop the parsley, leaves and stalks. Coarsely grate the cheddar.

Preheat your grill to high. Put a frying pan on a medium heat. Add 1 tbsp olive oil and the spring onions. Season with a pinch of salt and pepper and fry, stirring, for 2 mins till glossy and lightly browned.

Add the lemon zest and 3/4 of the parsley to the spring onions. Cook and stir for 1 min. Tip in the baby leaf spinach and squeeze in the juice form half the zested lemon. Cook, stirring, for 2-3 mins till the spinach has wilted.

Turn the heat under the pan down to low. Scoop the crème fraîche into the pan and add half the grated cheddar. Warm through gently, stirring, for 2 mins till just stemaing. Taste the sauce and add a pinch more salt and pepper if you think it needs it.

Tip the fish pie mix into the pan and gently stir to coat in the sauce. If your frying pan is suitable for going under the grill, scatter the remaining cheese over the top and then grill for 8 mins till golden and bubbling. If the frying pan isn't grillproof, transfer the fish and sauce to a heatproof dish, scatter over the cheese and grill.

While the gratin grills, squeeze 1/2 tbsp lemon juice intoa mixing bowl and add 1/2 tbsp olive oil and a pinch of salt and pepper. Whisky to make a dressing then toss in the salad leaves to lightly coat. Serve the hot fish pie gratin in warm bowls or on warm plates, garnished with the last of the parsley and with the salad on the side.