roasted cauliflower and garlic soup with caramelized onions

roasted cauliflower & garlic soup with caramelized onions // brooklyn supper

As the days and weeks add up, as the fall seems to have gone from just beginning to full-on, I’m feeling a little stunned. I’ve loved every minute of the mild early fall weather. Now that things have edged colder, and I find myself a little bewildered even thinking of coats. But, the occasional blast from the heater, my withered garden, and all these pumpkins seem to point to the inevitable. Soup weather, we meet again.

Food bloggers are supposed to give concise instructions for easy recipes, but, even with a totally hectic schedule that could really benefit from a few easy recipes, efficiency has never been my forte. I love the details of cooking, the textures, colors, and time. And so, this is a rather slow and meandering recipe for roasted cauliflower and garlic soup. It starts with a homemade vegetable broth, filled with remnants of a neglected refrigerator. The recipe stumbles toward completion only to be halted by irresistibly crisp caramelized onions that cook, ever so slowly, in a pan for two and a half hours. Though this kind of time is hard to come by, I promise you that on the right cold day, the hours spent, the creaking of the hot oven and stove, will be kind of perfect, and in exchange for your efforts, you’ll have a bowl of velvety cauliflower soup, with hints of smoke and garlic topped with crunchy, sweet onions, and nutty mushrooms.

Since preciousness isn’t really my thing, please feel free to spite me and keep things simple by just roasting the vegetables, pureeing them with a box of stock, and then topping the soup with a twenty minute version of caramelized onions.

crispy caramelized onions // brooklyn supper

roasted cauliflower & garlic soup with caramelized onions // brooklyn supper

Before we head to the recipe, I wanted to share a few fall-themed recipes we’ve been working on for a sponsored campaign for Target over on Babble Food. For your fall food enjoyment, we’ve got a roasted carrot hummus, seasonal flatbread pizzas, and jack-o-lantern oatmeal raisin cookies with cacao nibs and citrus zest.

Roasted Garlic and Cauliflower Soup with Mushrooms and Caramelized Onions
serves four to six

Though this recipes takes some time, there’s very little actual work involved, so try to think of it less like cooking and more like minding. I give my rich vegetable broth recipe below, but please feel free to make something easier or go with the boxed stuff if you need to.

for the broth (optional)
4 tablespoons olive oil
1 large red onion, quartered
4 carrots, washed, trimmed, and cut in half
6 stalks celery, trimmed and halved
1 bunch kale stems
1 bunch parsley stems
6 cloves garlic, smashed and peeled
4 teaspoons sea salt, or to taste
20 peppercorns
4 bay leaves
4 quarts water, plus more as needed

In a big stock pot, heat the olive oil over medium-high heat. Add the onion and sear. Next, add the carrots and celery and cook for a few minutes more. Add the stems, garlic, and spices. Pour in 4 quarts water. Bring to a boil, and then turn heat to a simmer. Cook, so broth is gently bubbling, for 3 – 5 hours. Strain, pour into jars, seal, and refrigerate.

(Aimee from Simple Bites has some great tips for freezing stock and broth in glass here.)

for the soup
1 large head cauliflower, cored and cut into 1/2 inch thick slices
1 head garlic, broken into cloves, ends trimmed and smashed, with the papery skin left on
3 tablespoons olive oil
2 tablespoons lemon zest
2 teaspoons sea salt
1 teaspoon ground black pepper
1 teaspoon ground cumin
1 teaspoon ground coriander
4 – 5 cups vegetable broth (see above)

Preheat oven to 400 degrees F.

Toss the cauliflower and garlic with the olive oil, zest, salt, and spices, and turn out onto a rimmed baking sheet. Roast for 25 minutes, or until the cauliflower is tender and the edges are lightly browned.

When it’s cool enough to handle, peel the papery skin from the garlic.

Using your blender of choice, puree the roasted vegetables with the broth until smooth. Check salt levels and adjust as needed. To serve, heat over medium-low heat, stirring often, for 20 minutes.

for the topping
1 red onion, sliced thin
4 tablespoons olive oil, divided
1/2 teaspoon sea salt, plus a pinch
8 crimini mushrooms, stems removed and sliced 1/4 inch thick
pinch of black pepper
3 tablespoons parsley, minced

Heat a medium-sized skillet over medium-high heat. Add 3 tablespoons olive oil, and then the onion slices and sea salt. Cook for 5 minutes, stirring often. Turn heat to low and cook, stirring occasionally, for 2 1/2 hours. After 1 hour they’ll be sweet but limp; after 2, delicious; but after 2 1/2 hours will they be crisp and sweet and perfect. Remove to a bowl.

Just before serving the soup, heat the remaining tablespoon of olive oil in the same skillet. Add the mushrooms, salt, and pepper, and cook for about 7 minutes, or until the mushrooms have given up their water and are crispy on the edges. Fold in the onions and parsley. Off the heat and set aside.

Ladle the soup into bowls, add the topping, and drizzle with olive oil.

The End.


  1. says

    as someone who has been knee deep in soup weather since, oh, say, august, i cannot thank you enough for this recipe. i’ve been in the need for some excitement in the soup realm! you had me at caramelized onions… nothing says fall like a house that smells of caramelized onions :)

  2. says

    I have everything but the mushrooms in my fridge. And a few loads of laundry to do. Seems it’s inevitable that this will be on my stove and in my belly in the next day or two. Looks gorgeous and I can’t wait to try.

  3. says

    Elizabeth, this soup looks so warm, comforting and creamy! Even better that there isn’t any cream involved. I’m bracing for colder weather but it’s nice to remember that I can make soups like this to warm me up from the inside.

  4. says

    I love how much care and thought was put into this soup. I am not a patient cook, but lately, I’ve been thinking about tackling the kind of food that needs an afternoon of slow cooking. Your recipe is a great reminder that a lot of the remarkably good stuff takes time.

  5. says

    Elizabeth, a meandering slow-going soup recipe is just what I want this time of year! I think the slow cooking really allows each layer of flavor to develop and the resulting soup is so much better than one quickly cooked in one go. On Sunday I spent hours tossing things into our big soup pot and it made me so happy. This fall weather makes me want to cozy up inside and make soups just like yours.

    • says

      Hi Abby, To optimize the flavor of the cauliflower, I think you’d still want to roast it. I don’t have a crock pot myself, so I can’t say with confidence how the rest of the recipe would translate. Thanks for checking out the recipe!

  6. Meghan says


    Recipe above still shows 4TBs of salt and sadly I just spent all day making the soup and it is beyond salty! I’ve literally tripled the amount of water but it has made the soup very thin, watery and still salty. :(

    I will definitely try to make this again another day, because it looks delish, but to save anyone that makes this A LOT of heartache and time, you may want to triple check that the recipe in the thread above is updated.


    • says

      Hi Meghan, Gah! I can’t tell you how sorry I am to hear this. I have fixed the broth recipe to read 4 teaspoons (not tablespoons), but I wish there was something I could do to fix your soup. Thanks for stopping in to let me know.

  7. says


    I just did this recipe and its absolutely delicious, I didn’t have any problems with the salt because I always put enough salt to my taste (that’s one bit I don’t follow from recipes)! Thanks for the delicious meal! :) (and btw the photos look gorgeous as well – I was trying to do the same but failed miserably :))

  8. Jennifer says

    I wish that your recipes were printer-friendly. What a shame to waste so much paper when it could be edited down to just a one-page recipe…eleven pages to get the recipe for a simple roasted soup seems crazy. Soup sounds delish, though! :)

    • Elizabeth says

      Hi Jennifer,
      Sorry to have used so much of your paper! Creating printer-friendly recipes is on my tech upgrade to-do list. One thing you could do is highlight the recipe text, copy it, and then paste it into a blank doc. That would give you more control with what to include. Hope that might help!

  9. Carolyn says

    It was cold and rainy in SoCal this weekend aka stay-in-and-make-soup weather. We made this recipe and finished it almost instantly. This is an absolute must make – healthy, easy and delicious!


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