Heat the oven to 200C/180C fan/ gas 6. Cut the squash in half lengthways, scoop out the seeds and set aside. Continue to scrape down the centre of both squash halves to carve out a roughly 2cm deep channel. If it’s tough, you can score with a knife and scoop out. Roughly chop the scooped-out squash and add to the seeds. Finely chop half the sage leaves. Pour the oil into a large roasting tin and stir in the chopped sage, mixed spice, mace and some seasoning. Tip the reserved seeds, chopped squash, squash halves and shallots into the tin and toss well. Roast for 30 mins until the squash and shallots are caramelised. Add the maple syrup, vinegar and pecans, and roast for 15 mins more until the nuts are toasted. Stir through the cranberries and leave to cool. Season well and set aside. Can be made up to a day ahead and chilled.

Meanwhile, tip the beetroot and feta into a food processor. Blitz to a smooth, thick paste, adding a splash of water if needed. Season with black pepper and chill. Can be made up to a day ahead and kept chilled.

Cut about a third of the pastry off and roll out on a lightly floured surface to an oval of about 25 x 16cm, making sure it fits the squash – roll it out a little more if needed. Transfer to a baking sheet lined with baking parchment. Spread a third of the beetroot mixture over the pastry, leaving a generous border. Pack the squash and shallot mixture into the cavities of the squash halves, and press down with your hands to ensure it’s well packed. Sandwich the squash halves together, then put in the middle of the pastry. Spread the remaining beetroot mixture over the top and sides of the squash so it’s completely covered. Brush the exposed pastry with beaten egg.

Roll out the second piece of pastry into an oval larger than the base, about 40 x 30cm. Lay the pastry carefully over the beetroot-covered squash, pressing down the edges lightly to seal, making sure you work from one end to the next so you don’t seal in too much air. Trim any excess pastry and, using a fork, press down all around the edges to seal. Cut any trimmings into leaf or star shapes to decorate the top, if you like. Brush beaten egg all over the wellington, top with the pastry decorations, if using, and brush with egg again. Sprinkle over the nigella seeds and a pinch of sea salt flakes

Chill, uncovered, for at least 30 mins, or up to 2 hrs. Heat the oven to 200C/180C fan/gas 6 with a baking tray inside to heat up. Carefully slide the wellington onto the tray. Cook for 40-45 mins until deeply golden. Leave to rest for 10 mins. You can freeze the wellington, uncovered, on a baking tray until solid, then wrap in cling film, then foil. Will keep frozen for two months.

While the wellington is resting, melt the butter in a pan over amedium-high heat. Once it starts to foam, add the remaining sage leaves and fry on each side for 30 seconds1 min until crisp. Arrange the leaves on the wellington and spoon over the melted butter. Cut into thick slices.