Preheat the oven to 200°C (gas 6). Put the frozen spinach in a saucepan, cover and cook over a low heat for 5 minutes or until thawed.
Meanwhile, put the potatoes in a pan of lightly salted water. Bring to the boil, then reduce the heat and cook for 15–20 minutes or until tender. Cook the cauliflower in a steamer, over the potatoes, for 10 minutes, or in a separate pan of boiling water.
Tip the spinach into a colander and press down with a vegetable masher to squeeze out excess liquid. Chop the spinach roughly and season with salt, pepper and nutmeg.
Drain and mash the potatoes with the milk and butter. Spread half the mashed potatoes in a 1 litre ovenproof baking dish (or six individual dishes). Layer the spinach on top of the potatoes.
Purée the cauliflower in a blender or food processor. Add the eggs and the remaining mashed potatoes and taste to check seasoning. Spread this mixture over the spinach layer.
Sprinkle the top with grated cheese, then put in the oven and bake for 30 minutes (20 minutes for individual dishes) or until golden. Serve hot, garnished with parsley, if liked.
*This could be served as a light lunch or supper dish for four. *Floury varieties of potato, such as King Edward or Maris Piper, are best for mashing. *If using fresh spinach, you will need 900g. Remove stalks and coarse midribs, wash thoroughly, then put the wet leaves into a covered pan without adding any extra water and cook gently for 5 minutes.