Cut the acorn squash in half and remove the seeds. Brush with olive oil and bake for 45 minutes at 350 °F. In a skillet, fry 2 chopped onions, with some garlic and season with salt. Add a dozen Paris mushrooms, sliced. In a bowl, mix cooked quinoa with the mushroom preparation, then use it to fill the squash and bake for 10 minutes. You can also sprinkle the squash with crumbled feta or mozzarella before baking.