Heat oil in a large stockpot over medium-high heat until shimmering. Add onion, carrots, and celery, and saute for about 5-7 minutes until the onions are cooked and translucent. Add garlic and saute for an additional 2 minutes until fragrant, stirring occasionally. Add remaining ingredients and bring to a boil. Reduce heat to medium-low, cover and let simmer for 10-15 minutes until all vegetables are tender. Season with salt and pepper if needed. Serve warm topped with blue cheese crumbles and green onions.