Heat 1 tablespoon of olive oil in a large saucepan over medium heat.

Add the diced red onion and sauté for 5 to 7 minutes, or until soft and translucent.

Stir in the diced carrots and celery, and cook for 7 to 10 minutes, or until tender.

Stir in the diced russet potato and frozen corn, and cook for 5 to 7 minutes, or until most of the liquid has evaporated.

Add the minced garlic, sage sprigs, and thyme sprigs, and cook for 1 minute, or until the garlic is fragrant.

Stir in the mushroom broth, nutritional yeast, white miso, and low-sodium tamari sauce, and bring to a boil.

Reduce heat to medium-low, and simmer for 20 to 25 minutes.

Meanwhile, heat the remaining 1 tablespoon of olive oil in a large skillet over medium heat.

Add the sliced white or cremini mushrooms, and sauté for 10 minutes, or until all liquid has evaporated and the mushrooms are browned.

Carefully blend the mushroom broth mixture in a blender in batches until smooth.

Stir in the sautéed mushrooms into the blended sauce.

Season with salt and pepper, if desired, to taste.