Prepare onions, carrots, celery, Brussels sprouts and winter squash; heat 2 tablespoons of oil over low heat in a soup kettle.
When ready to sauté, increase heat to medium-high and add onion, carrots, and celery; sauté until softened, about 5 minutes. Stir in thyme and then couscous, followed by broth; cover and bring to a simmer. Reduce heat to medium-low and continue to simmer until most of the liquid has absorbed but dish is still moist, about 10minutes.
While couscous cooks, place Brussels sprouts (cut side down) and squash in a large (12-inch)skillet with remaining 1 tablespoon of oil, 1/4 cup of water, and a sprinkling of salt and pepper. Cover skillet, turn burner to high, and heat until vegetables start to steam. With skillet still covered, cook until all of the liquid has evaporated and vegetables start to sauté, about 5 minutes. Remove lid and continue to cook until vegetables turn golden brown, a few minutes longer.
Stir in vegetables, kale and optional cheese into the couscous and cook to wilt kale and blend flavors, a couple of minutes longer. Adjust seasonings, including salt and pepper to taste. Serve with an optional sprinkling of cheese.