Preheat the oven to 190°C, 170°C for a fan assisted oven.
Carefully slice a thin layer from the tops and tips of each onion, peel away the papery outer skin and discard.
Slice each onion in half across the centre. Gently push up from the trimmed base of each onion, pushing out the middle layers so that the centres are hollow and you have only two outer layers of each onion remaining. Slice a piece from each of the removed onion centres to cover any holes in the base of your hollowed onions. You should now have four onion ‘cups’.
Arrange the onion cups across a shallow oven tray and drizzle with the melted coconut oil. Transfer to the oven for 10 minutes so that they begin to soften.
Whilst the onion is cooking, thoroughly rinse the squash seeds, removing any stringy flesh and pat dry.
Take the centre layers from one of the hollowed onion halves and finely dice. Reserve the remaining onion for a further meal.
Heat the tablespoon of coconut oil in a frying pan over a medium heat. Add the diced onion, garlic, squash, mushrooms, chestnuts, cranberries, rosemary and sage. Season well with salt and pepper and stir well to combine. Sweat for 3-4 minutes until just tender.
Add the nutritional yeast to the pan and stir well to combine.
Keeping the onions on the tray, divide the stuffing mixture evenly between each.
Arrange the squash seeds across the tray, next to the onions, and season with a little salt and pepper, spooning over the oil from the tray.
Return to the oven to bake for a further 15-18 minutes until the onion is tender, the stuffing is piping hot through and the squash seeds are golden.
Top each stuffed onion with a sprinkling of squash seeds to serve.