Spinach bread and butter casserole

16 oz fresh leaf spinach
1 day-old ciabatta loaf, thinly sliced
4 tbsp softened butter or olive oil
1 red onion, thinly sliced
4 oz mushroom, thinly sliced
2 tbsp olive oil
1 tsp cumin seed
1/2 tsp dried thyme
salt and ground black pepper
4 oz Gruyere or Gouda cheese, grated
3 eggs
2 1/4 cups milk
fresh nutmeg, grated

Rinse the spinach well and blanch it in the tiniest amount of water for 2 minutes. Drain well, pressing out any excess water, and chop. Spread the bread slices thinly with the butter. Grease a large shallow ovenproof dish (9 x 13 in) and line the base and sides with bread.

Fry the onion, mushroom and thyme in the oil for about 5 minutes then add the cumin seeds and spinach. Season well. Layer the spinach mixture with the remaining bread and half the cheese. For the top, mix everything together and sprinkle over the remaining cheese.

Beat the eggs with the milk, adding seasoning and nutmeg to taste. Pour slowly over the whole dish and set aside for a good hour or overnight to allow the custard to be absorbed into the bread.

Preheat the oven to 375 F. Stand the dish in a roasting pan and pour around some boiling water for a bain marie. Bake for 40-45 minutes until risen, golden brown and crispy on top.