Step 1

Preheat the oven to 375°F. Halve the squash laterally through the center (rather than through the stem), and scoop out the seeds.

Step 2

Place the squash in an 8×8-inch baking dish with the cut side down, and fill the baking dish with ¼ inch of water.

Step 3

Loosely cover with foil and bake until the squash and edible skin are totally soft, about 35 minutes. Set aside.

Step 4

Combine the quinoa and 1 cup of water in a small pot and bring to a boil over high heat. Reduce the heat to low, cover, and simmer for 15 to 20 minutes. Remove the pot from the heat and let cool; then fluff the quinoa with a fork.

Step 5

Preheat a large skillet over medium heat for about 1 minute. Add the onions and sauté for about 7 minutes, stirring often, or until the onions turn nice and brown, which brings out the sweetness and gives the dish a nice deep flavor. Add water 1 to 2 tablespoons at a time, to keep the onions from sticking to the pan.

Step 6

Add the mushrooms, celery, cabbage, salt, and pepper to taste, and cook for 5 more minutes, stirring occasionally.

Step 7

Add the vegetable mixture to the quinoa and stir together.

Step 8

Fill each of the cooked squash halves with the quinoa mixture, packing them firmly to fit as much of the mixture into each half as possible.