Preheat your oven to 375°F (190°C) and line a baking sheet with parchment paper.

Gently clean the portobello mushrooms with a damp cloth and remove the stems and gills. Brush each mushroom cap with olive oil, and season with salt and pepper.

Combine quinoa with water or broth in a saucepan. Bring to a boil, reduce heat to low, cover, and simmer for about 15 minutes until fluffy.

In a skillet, heat olive oil over medium heat, add butternut squash and sauté for 8-10 minutes. Add garlic and thyme for an additional 1-2 minutes.

In a mixing bowl, combine cooked quinoa, sautéed butternut squash, cranberries, and walnuts. Mix thoroughly.

Stuff each mushroom cap with the filling, pressing gently. Top with Parmesan cheese.

Bake the stuffed mushrooms for 20-25 minutes until tender and cheese is melted.

Let the mushrooms cool for about 5 minutes before serving as a main dish or hearty side.