Add the ½ c butter and ½ c Sage, Mushroom, & Garlic Olive Oil to a large skillet. Heat over medium heat until the butter is melted. Add the onions, mushrooms, and celery and cook for ~10 min, stirring occasionally, until the celery is soft, the mushrooms and turning color, and the onion is turning translucent. Add the garlic and cook 2-3 min more, until the garlic is nice and fragrant. Transfer the warm vegetables to the bowl of bread cubes, scraping out the skillet completely as you do so.