1. Preheat over to 400F/200C.
2. Cut squash in half lengthwise and scoop out seeds. Brush flesh with olive oil and sprinkle with salt.
3. Place squash cut-sized down on a baking tray. Roast for about 20-30 minutes until flesh is easily punctured with a fork.
4. Add vegetable stock and quinoa to a pan and bring to a boil, then reduce to a simmer, cover and cook until all the stock is absorbed.
5. Add mushrooms and garlic and sauté for a few minutes.
6. Add cooked quinoa and sauté for a minute or two.
7. Add the spinach and allow to wilt, stir gently to combine.
8. When the squash has finished cooking, allow to cool slightly then add the filling.