In a large pot, warm the oil over medium heat. Add onion and sauce until translucent.
Pour in the broth and bring to a boil. Add the potatoes, rosemary and the bay leaf. Cover partially, reduce the heat to low, and simmer for 15-20 minutes.
Remove the pot from the heat and discard the bay leaf. Puree the soup with a blender or immersion blender.
Bring the soup to a simmer. Add coconut milk. Season with salt and pepper and serve.