Preheat oven to 350 degrees F. Cut each squash lengthwise in half. Scoop out the seeds and discard. Trim a little from the uncut side so the squash will sit flat once stuffed. Place squash halves, cavity side down, on a non-stick or parchment-lined baking sheet. Cover and bake for 35-45 minutes, or until firm/tender. Meanwhile, prepare filling by heating the olive oil in large skillet over medium heat. Add the shallots, garlic, mushrooms, bell pepper and carrots and cook until the mushrooms are very tender, about 5-6 minutes. Place mixture in a bowl; mix in all remaining ingredients. Turn the squash halves, cavity side up, on the baking sheet. Spoon and mound the mushroom mixture into the centre of them. (Can be cooled to room temperature at this point, stored in the fridge and baked later.) Cover and bake 15-20 minutes, or until the squash is tender and the filling is heated through.