Put the spinach in a colander, pour over a kettle of boiling water until the spinach wilts, then drain and squeeze out as much liquid as you can (you might need to do this in two batches).
Put the spinach in the bottom of a gratin or baking dish, season, then sprinkle with nutmeg.
Drape the prosciutto over and around the spinach, then sit the tomato halves on top, cut-side up. Dot the crme frache over the whole dish, scatter with the goats cheese, then season with more pepper.
Bake for 10-15 mins until the cheese is melting into the crme frache and the edges are starting to bubble. Scoop out of the dish and serve with crusty bread and a green salad.
