Preheat the oven to 210C/ 200C fan*/gas mark 6 ½. Place a third of the spinach in an ovenproof sauté pan or deep frying pan with 1 tbsp water, and set over a medium heat. As it wilts, add the rest. When it has all gone completely soft, lift out with tongs. Get rid of the water left behind in the pan, and wipe it.