Halve the squash, seed and trim the bottoms so they sit flat on the sheet pan.
Lightly brush with olive oil and season with salt and pepper.
Lie the squash FACE DOWN on the cookie sheet, covered with tin foil and bake for 35 minutes or until tender.
Meanwhile, cook the rice according the package instructions.
Saute the onion and mushrooms until tender. Add to the cooked rice.
Remove the squash from the oven and raise the temperature to broil.
Scoop out some of the flesh from the squash and add to the rice mixture. Add the 1/2 Cup of vegetable broth to this and place in the cavity of the squash. Top with parmesan. Broil for 2 minutes or until cheese is melted and just starting to brown.