Preheat oven to 425°F. Line baking sheet with parchment paper. Toss the cauliflower florets with 2 tablespoon olive oil and some salt. Spread in even layer on baking sheet. Roast for 30-35 minutes or until edges are browned.
In a large Dutch oven, heat remaining 2 tablespoon olive oil over medium heat. Add the onion and cook for 5-7 minutes or until translucent. Stir in the garlic and cook for another 30 seconds.
Add vegetable broth and roasted cauliflower to Dutch oven and increase heat to medium-high until it begins to simmer. Reduce heat to maintain a simmer and cook for 20 minutes.
Using either an immersion blender, or transferring the soup in batches to a traditional blender, puree the soup until smooth. If using blender, be careful to not fill it very full or it will splatter everywhere.
Stir in milk, Parmesan cheese, butter, lemon juice, salt and nutmeg and cook for another 2 minutes.
Serve immediately and top with some fresh thyme and roasted chickpeas if desired.
Roasted Chickpeas
Preheat oven to 350°F. Line baking sheet with parchment paper.
Rinse and drain chickpeas and pat dry with paper towel. In a medium bowl, toss chickpeas with olive oil and spices so they get coated. Spread evenly on baking sheet.
Roast for 45-50 minutes or until golden brown and crispy to the touch. Turn the pan around and shake the chickpeas at the halfway point to help cook them evenly.
Notes
You can steam your cauliflower if you want but by roasting the cauliflower, you are building flavor by adding caramelized notes.
Sautéing the onions and garlic before adding broth and roasted cauliflower is just another additional flavor profile.
Use quality vegetable broth or chicken broth if you don't need it to be vegetarian. Broth is a huge component in the cauliflower soup recipe.
Use an immersion blender to puree until smooth. If you don't have one, using a blender is fine but you have to do it in stages which I don't like.
Add butter and milk for creaminess. If you are vegan, then skip these ingredients and add an extra cup of vegetable broth.
A pinch of nutmeg makes all the difference in the warmth of the soup.
Top with some crispy chickpeas or additional roasted cauliflower for texture in the cauliflower soup.