In large dutch oven or stock pot, melt 2 tablespoons of butter over medium high heat. Add garlic and cook for 30 seconds or until fragrant. Add red bell pepper and carrots and cook for 10 minutes or until pepper softens.
Add potato, cauliflower, vegetable broth, milk, bay leaf, thyme and kosher salt. Bring to boil, then reduce heat to simmer and cook for about 10-12 minutes or until cauliflower and potato are softened. Turn heat to low.
Meanwhile, rinse 2/3 cup quinoa in cold water and place in small pan and cover with 2 cups of cold water. Season with pinch of kosher salt and bring to boil. Reduce to simmer and cook until quinoa is softened. Fluff with fork and set aside.
Ladle about 3 cups of broth and vegetables, mostly potatoes and cauliflower but leaving some in pot for texture, into high sided container and blend with a blender until smooth.
Add back to pot. Remove bay leaf and season with more salt if desired. Add quinoa and remaining tablespoon of butter and cook for another 5 minutes. Quinoa and butter will thicken soup as quinoa absorbs some of liquid. Serve immediately.
