Heat the oven to 200C/180C fan/gas 6. Using a serrated knife, cut a small disc off the bottom of each squash so they stand upright on a baking tray. Slice off the tops (these will be used as lids), and scoop out and discard the seeded centre. Rub 2 tbsp oil on the inside and outside of the squashes, then season.

Tip the dried mushrooms into a heatproof bowl and cover with 100ml boiling water. Cover and leave to soak for 15 mins. Meanwhile, heat the remaining oil in a non-stick frying pan, and cook the shallots for 10 mins until softened and translucent. Drain the rehydrated mushrooms (reserving the soaking liquid) and roughly chop, then add to the pan along with the chestnut mushrooms. Fry for 10 mins more. Stir in the garlic and cook for another minute. Add the stock, most of the reserved soaking liquid (leave the last few drops in the bottom of the bowl, as this may contain grit) and the grains, and bring to the boil. Remove from the heat and stir in the crème fraîche, tarragon and cheese. Season.

Divide the filling between the hollowed-out squashes. Put the ‘lids’ on top and bake for 1 hr-1 hr 10 mins, depending on the size of the squash. When ready, the squash skins should be blistered and the flesh soft and cooked through. Leave to rest for 10 mins before serving.