2 x 285g jars charred roasted peppers in oil, drained well and all oil reserved
1 onion, chopped
200g button mushrooms, sliced
180g ready-cooked (vacuum-packed) whole chestnuts
2 garlic cloves, chopped
½ tsp paprika
8 thyme sprigs
200g spinach leaves
¼ tsp freshly-grated nutmeg
For the pesto
3 garlic bulbs, halved through their middles
1 red chilli, seeded and roughly chopped
100g pecans, lightly toasted
Preheat the oven to 190°C, fan 170°C, gas 5. Scoop out the seeds with a soup spoon or melon baller after halving the butternut squash vertically. Nonstick baking paper should be used to line a roasting tin large enough to hold both squash halves. Place both pieces in the roasting tin, cut sides down, and roast for 50 minutes, or until just cooked.
Allow it cool for 15 minutes before carefully turning the squash halves over and scooping out the insides along the length of each half, leaving a 3cm squash border all around the edge. Make sure you don't pierce the skin. Season the hollowed-out squash halves with salt and pepper and set aside the scooped-out squash.
2 tbsp oil from the canned peppers in a large saucepan set over medium heat while the squash halves cook Add the chopped onion and simmer, stirring frequently, for about 8 minutes, or until soft and just starting to colour. Cook, stirring frequently, for 5 minutes, or until the mushrooms are browned and tender.
Break the chestnuts down with a fork or a potato masher. Rather than being entirely broken down, they should be lightly crushed. In a large skillet, combine the crushed chestnuts, 2 minced garlic cloves, paprika, and the leaves from 2 thyme sprigs. Cook for a minute more. Stir in the squash that has been scooped out, stirring to combine and break it down evenly. Season to taste, then remove from the fire and mix in the finely chopped parsley.
Separately, wash and drain the spinach. Transfer to a large saucepan and wilt, stirring frequently, over medium heat. The leaves should crumble in about 2-3 minutes. Using a clean tea towel, wring out any extra damp before seasoning with salt, pepper, and nutmeg.
Line the hollowed-out squash halves in an equal, single layer with the drained, chargrilled peppers. Distribute the mushroom and chestnut mixture evenly between the two sides. Spoon the spinach evenly over the squash filling in one half. Make a butternut squash form out of the two halves by tying them together numerous times along the length of the squash with kitchen string. Return the roasting tin to the oven.
Bake for 20 minutes, then add the half garlic heads and remaining thyme sprigs to the tin, dripping 1 tbsp oil from the pepper jars over them. Bake for 30-40 minutes more, or until the squash is totally soft and heated.
To prepare the pesto, squeeze the garlic cloves from one split garlic bulb and combine with the red chili, nuts, and roughly chopped parsley in a small food processor bowl. Blitz everything together, pausing to scrape the sides down. Add the leftover oil from the pepper jars in a steady stream while the motor is running. A sloppy pesto will emerge. To taste, season with salt and pepper.
Remove the thread from the squash and slice it thickly. Serve with the pesto on the side and the garlic bulbs to garnish.