Heat The Spicy Olive's Butter olive oil in a large Dutch oven over medium heat. add onion, thyme, salt and garlic. Cover and cook, stirring occasionally until onion is very soft and beginning to caramelize, about 10-12 minutes
Add flour to Dutch oven and cook stirring constantly for 1 minute. Add vegetable stock and diced potato. Increase heat to high and bring to a boil. Stir until vegetable broth has thickened. Add cauliflower and reduce heat to medium. Cook uncovered until potatoes and cauliflower are tender, about 20 minutes.
Use an immersion blender to blend soup until thick and smooth. Can also use a blender to do this. Do in batches and be very careful as the mixture can spit and cause burns. Make sure to leave blender lid loose or leave out center and cover with a towel to allow steam to escape.
Ladle into soup bowls and enjoy!
If you are not concerned about being vegan this soup is delicious with crumbled bacon and scallions.