Preheat oven to 350F/170C.

Cut squash in half lengthwise. Using a sturdy metal spoon, scrape out and discard seeds. Score the flesh inside the neck and scraping out the flesh in center and neck until each side of the squash is hollowed. Leave at least an inch of flesh around the rims so that the squash holds up when baked. Chop the squash pulp and set aside.

In a large skillet over medium heat, heat the olive oil and cook the onion, chopped squash pulp, garlic, chili, and salt for about 5 minutes, until the onions and squash are tender. Add fresh mushrooms, and herbs. Drain the dried mushrooms, reserve liquid, and add them to the mixture. Continue cooking, stirring occasionally, until mushrooms are lightly browned, about 8 minutes. Transfer to a bowl and let cool. Mix in the toasted breadcrumbs and season with additional salt, pepper, and herbs, as desired.

Spoon stuffing into squash cavities, packing in as much as you can fit. Place halves back together and tie tightly with kitchen twine to secure. Brush with olive oil and sprinkle lightly with salt. Place squash on a baking sheet and bake for 30 minutes. Flip, cover with foil, and bake until soft, 30 to 45 minutes longer. Slice crosswise into rounds and serve hot.