Preheat your oven to 400°F (200°C).

In a medium pot, bring water to a boil and add the peeled and cubed butternut squash. Cook for about 10 minutes or until tender. Drain thoroughly.

Heat 1 tablespoon of olive oil in a large skillet over medium heat. Add the chopped onion and sauté for 3-4 minutes until translucent.

Stir in the minced garlic, dried sage, dried thyme, salt, and black pepper. Cook for an additional minute.

Incorporate the cooked quinoa, butternut squash, dried cranberries, and chopped walnuts into the skillet. Mix well.

Brush the portobello mushrooms with the remaining tablespoon of olive oil. Place them on a baking sheet, gill side up.

Spoon the filling into each portobello mushroom cap, pressing down lightly.

If using feta cheese, sprinkle it on top of each stuffed mushroom.

Bake for 20-25 minutes until the mushrooms are tender and the tops are golden brown.

Remove from the oven and garnish with chopped parsley before serving.