Set a large 6-quart soup pot over medium heat. Add the oil, chopped onions, and garlic. Sauté for 3 minutes. Then stir in the cauliflower and sauté another 5-7 minutes, stirring occasionally so the garlic doesn't burn.
Pour the vegetable broth and buffalo sauce into the pot. Cover and simmer the soup for at least 20 minutes, or until the largest cauliflower florets are fork-tender.
Carefully pour the hot soup into a blender jar. Add the cream cheese and shredded cheddar. Place the lid on the blender, and open the vent in the lid. Place a dish towel over the blender so the steam can vent, but you do not get splashed with hot soup through the open vent. Then blend until completely smooth.
Taste, then season with salt and pepper as needed. Serve warm sprinkled with extra cheese, scallions (or bacon if you're a meat eater)!