Cook the onion and garlic on medium low heat in the butter (or oil) until translucent and soft. Add the flour to make a roux, stir and add 1 cup of broth. Add the garlic and onion powders and stir to incorporate. Add the remaining 5 cups of broth and cauliflower. Cover and bring to a boil on medium heat, then lower to medium-low and let simmer for about 30 minutes or until you can piece the cauliflower easily with a fork. Purée with an immersion blender or in a regular blender. Keep blending even if you think it’s ready. The smoother it is, the creamier and better it is. It’s like liquid velvet. Stir in the grated cheddar until melted and incorporated. Serve with pepper, and salt if you like it (but I didn’t think it needed it at all).