Fresh spinach needs only the very briefest cooking, to keep its colour and texture.
If necessary, place spinach in a bowl of cold water, and leave for a few minutes until any grit drops to the bottom, or rinse under cold running water in a colander. Drain well.
Heat a little olive oil in a large frying pan.
Add the drained spinach, and allow to cook for about a minute, turning frequently.
Add a knob of butter, season and sprinkle with freshly grated nutmeg. Toss together until the butter melts and serve immediately.