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Caramelized Onion & Roasted Cauliflower Soup

April 18, 2011

This past weekend, I posted an incredibly delicious Caramelized Onion & Roasted Cauliflower Tart. It’s so delicious, in fact, that it inspired me to make this soup. The result was an entirely different dish than the tart, and yet it captures all the rich, delicious flavors of the tart—only without the all the cream and the eggs, and with a whole lot less cheese. The flaky, butter crust has also been nixed, thus saving your arteries 6 tablespoons of butter. Don’t get me wrong, this soup still tastes incredibly rich and decadent. And it’s not exactly diet food. But it is a whole lot lighter than it’s cousin, the tart. You’ll be saving on calories in a pretty major way—because we can’t be eating tarts everyday, people—but you won’t feel like you’re depriving yourself of anything.

Other than being downright delectable, this soup is a testament to allowing yourself to experiment in the kitchen. Until somewhat recently, I was a bit afraid of experimenting, with the result that I followed recipes pretty closely. I mean, if the recipe really would be better with a little of this, or more of that, or none of the other, then surely the recipe would have a little of this, or more of that, or none of the other. Right?

Wrong. Totally wrong, as I’ve come to realize in the course of my cooking adventures. Most recipes can be improved upon, and you shouldn’t be afraid of just going with your instinct regarding what a recipe needs to make it better, or how one recipe could be used to create something entirely new. The more I’ve cooked, the more comfortable I’ve become with changing recipes on a whim, and/or creating entirely new recipes. It’s fun, liberating, and usually results in a very yummy meal.


Serves 4 as a main

For the soup:

1 large head of cauliflower (about 1 lb.)
1 large yellow onion
3-4 cups mild vegetable broth or low sodium chicken broth
2/3 cup grated gruyère cheese
1/3 cup mascarpone
whole grain mustard (to taste)
truffle oil (optional)
chopped fresh, flat leaf parsley (for garnish, optional)
olive oil
salt & pepper

For the crostini:

a rustic baguette
whole grain mustard
shredded Gruyère cheese

Preheat the oven to 400°F.

Remove the stem and outer leaves from the cauliflower, and cut into florets. Place on a rimmed baking sheet, and toss with a little olive oil (about 1-2 tablespoons), salt, and pepper (to taste). Roast, tossing occasionally with a spatula, until just starting to turn golden at the edges—about 20 minutes. Remove from oven.

While the cauliflower is roasting, caramelize the onion. Halve the onion, then thinly slice. In a large pot or dutch oven over medium-high heat, heat a couple splashes of olive oil. Add the onion, along with a little salt and pepper. Cook (stirring occasionally) for about 7 minutes, until the onion is translucent and just beginning to turn golden. Reduce the heat to low, and cook (stirring occasionally) until the onions are a deep golden color and caramelized, about 15-20 minutes.

While you’re waiting on the onions and the cauliflower, prepare the crostini. Cut the baguette into 1/2 slices. Arrange the slices on a rimed baking sheet (I like to line mine with parchment paper to catch any melted cheese). Spread a little whole grain mustard on top of each slice, and then top with a little grated gruyère cheese. Set aside until you’re ready to toast them—you’ll do this at the last minute, after the soup is ready.

Once the onions are caramelized, add the roasted cauliflower to the pot, along with 3 cups of broth. Simmer everything together for a 2-4 minutes, so that all the flavors mingle.

Remove the soup from the heat, and get out your immersion blender.* Blend the soup, using the immersion blender, until it’s smooth and creamy. Next, add the mascarpone, gruyère, and 1 teaspoon whole grain mustard. Stir until the cheeses are melted and incorporated into the soup. At this point, taste for seasonings. Add salt, pepper, and more whole grain mustard (all to taste) and, if you feel that the soup is too thick, add a little more broth to reach your desired consistency. Finally, blend everything together one more time—this will ensure that the mascarpone and gruyère are well-incorporated, and that the soup is nice and smooth.

Now it’s time to finish off those crostini. Pop the baking sheet under your oven’s broiler, and broil the crostini until the cheese is bubbling, and the edges of the bread are turning golden brown. Remove from the oven.

Ladle the soup into bowls. Garnish with a light drizzle of truffle oil, the chopped parsley leaves, and a couple crostini. Enjoy!

* If you don’t have an immersion blender, you can purée the soup in batches in a food processor or blender. But immersion blenders are a wonderful kitchen tool. Read about why I think everyone should have one here.

5 Comments leave one →
  1. April 18, 2011 10:28 am

    Yum. I am going to try it minus the cheese…I bet it is stil amazing!

  2. April 19, 2011 11:32 am

    This looks gorgeous! Thanks for stopping by my blog so glad to have found you. I’m especially loving the indian hash browns 😀

  3. Tuva permalink
    April 27, 2011 8:47 am

    Hi Kirsten!
    Love your blog! the roasted cauliflower soup was fantastic!:) Thank you for sharing!
    Tuva(Mirjams friend from Norway, we met in Oslo once:)

    • April 28, 2011 1:25 pm

      Hi Tuva! Thanks so much – I’m so happy that you like the blog, and the soup! I of course remember meeting you in Norway! Hope that all is well with you. 🙂


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