"Have ready an ovenproof dish or roasting pan at least 2 litre · 3½ pt capacity (for example 20cm x 30cm · 8in x 12in) or similar.For the filling, heat a tablespoon of oil in a large casserole over a medium-high heat, season the chicken pieces and colour on both sides, half at a time. Drain off the fat, return all the pieces to the pan, add the wine and simmer to reduce by half. Pour in the stock or water. Bring to a simmer, cover and cook over a low heat for 30 minutes, stirring halfway through.At the same time, melt the butter in a large pan over a low heat. Add the onions, sprinkle over a teaspoon of sea salt and gently fry for 30 minutes, stirring frequently to prevent colouring. By the end they should be silky and soft.Meanwhile, place the washed spinach in a large pan with just the water that clings to the leaves, cover and cook over a low heat for about 10 minutes, stirring halfway through, until it wilts. Drain in a sieve, pressing out any excess liquid with a spoon or potato masher, and coarsely chop.Remove the chicken to a bowl and leave the juices to settle. Skim off and discard the fat that rises to the top, reserving the juices. Once the chicken is cool enough to handle,remove and discard the skin and coarsely shred the flesh.In a blender, purée the onions with 150ml · 5fl oz of the reserved cooking juices, combine this with the shredded chicken in a large bowl, fold in the spinach then transfer the filling to the ovenproof dish.For the mash, cut the pumpkin flesh into chunks. Cook for 15-20 minutes until tender either in a steamer or in a large covered pan with a couple of centimetres of water. Drain in a sieve and press out excess liquid using a potato masher. Transfer to a large bowl and coarsely mash using a fork. Dice and stir in the butter, the olive oil, nutmeg and some salt and pepper, then fold in the parsley. Smooth this on top of the chicken filling, sculpting or forking the surface into rough peaks. You can make the pie to this point in advance, in which case leave to cool, cover and chill.Preheat the oven to 210C/190C fan/gas 6½ and bake the pie for 45 minutes. Heat the grill, dot the top with a little butter and pop underneath until golden at the tips."