Gently heat the olive oil in a large pot over medium heat.
When the oil is hot, but nowhere near smoking, add the onions, carrots and celery.
Cook the vegetables gently for 5 minutes, stirring frequently.
Add the garlic to the pot and cook for 1 minute while stirring.
Add the pumpkin, zucchini, potatoes and sweet potatoes to the pot. Cook for 1 minute, while giving everything a good stir.
Add the vegetable broth to the pot.
When the broth is hot and steaming, add the vegetable base and the turmeric powder. Stir well until the vegetable base is dissolved and the turmeric is incorporated.
Raise the heat to high and bring the broth to a boil. When the broth is at a full bowl, lower the heat to medium-low and cover the pot.
Simmer the soup for approximately 30 minutes, stirring occasionally.
The vegetables should be very tender. They should fall apart when pressed with a spoon or pierced with a fork.
Taste the broth and add salt, if need. As a reference, we added 1 teaspoon to our creamy vegetable soup.