Heat the oil in a large saucepan over medium heat. Cook the onion and carrot until onions are transparent and fragrant. Add in the potato, celery salt and pepper. Mash the potato into the other vegetables and mix well.
Add in the broccoli and vegetable broth. Mix in the butter, then cover and reduce heat, allowing the soup to simmer for around 20 minutes.
Mix in the cream and cheese. Allow to simmer for around 5 minutes, or until the cheese has melted. Turn off the heat and let sit for around 7 minutes before serving. The soup should thicken slightly as it cools.