:
Heat the olive oil in a small saucepan over medium heat.
Add the carrots, celery, onion, mushrooms, and garlic to the pan and sauté until the vegetables are soft, about 5-7 minutes.
Pour the vegetable broth into the pan and bring the mixture to a boil.
Reduce the heat to low and simmer until the vegetables are fully cooked, about 10-15 minutes.
If using, add the cooked rice to the pan during the last 5 minutes of cooking.
Season the soup with salt and pepper to taste.
Serve hot and enjoy your single serving of delicious vegetable soup!