Turn the grill on to high. Boil the kettle. Defrost the spinach in a bowl in the microwave. Peel and finely chop the onion, and place in a large ovenproof frying pan on a high heat with 1 tablespoon of olive oil. Cook for 5 minutes, or until soft, stirring regularly. Cook the pasta in a pan of boiling salted water for 8 minutes, until al dente, then drain, reserving a mugful of starchy cooking water.

Stir the flour and mustard into the onions, then gradually stir in the milk. Add the spinach to the pan, water and all, then season to perfection. Stir in the fish chunks and simmer for another 5 minutes on a medium heat, then stir in the drained pasta, along with a splash of reserved water, if needed. Coarsely grate and mix in half the cheese, grating the rest over the top. Carefully transfer to the highest shelf of the grill for a few minutes, or until golden and bubbling.

Meanwhile, finely slice the chicory bases and separate the leaves, toss with the rocket and 1 tablespoon each of red wine vinegar and extra virgin olive oil, then season to perfection. Serve with the fish pie pasta bake.