Caramelized Onion & Kale Soup au Gratin

Caramelized Onion & Kale Soup with Roth Alpine-Style Cheese | Big Girls Small Kitchen

This is the soup that needs no introduction. The dish that launched (maybe?) the soup and grilled cheese pairing. Plus kale.

The best thing you can do for onion soup is decide yesterday you’ll probably crave a bite today. If you make broth, caramelized onions, and, for this particular rendition, kale when you have that realization, then when you–surprise!–want the soup, you can actually have it in almost no time and with almost no work. Now this is cooking.

I can’t remember a time I didn’t love onion soup. The sweetness of the onions and the richness of homemade broth (usually: beef; here: chicken) is perfect together from the start.

Even more perfect? The way that good bakery sourdough bread absorbs some of that goodness right from its toasty underside. On its crispy top, the final flavor note is rich, nutty alpine-style cheese–I use the aged Wisconsin cheese, Roth Grand Cru. I didn’t invent the combination, but I could easily celebrate it weekly.

Though I’m accustomed to serving a rich, whole-meal soup like this with a green salad alongside, here I added garlicky kale right into the soup, turning classic French Onion Soup into a truly current one-pot/four-crock meal.

Though I ate onion soup growing up, these days I think of it as a romantic dish, rather than a homey or nostalgic one, probably because Alex loves it so much. That’s one of the most fun parts about cooking for someone you love: customizing every bite to suit his or her fancy. So, here’s a Valentine’s Day suggestion for you, if your loved one loves onion soup: prep the three parts and pick up some cheese on February 13th and start cooking early.

This post is sponsored by Roth Cheese, an alpine-style cheese crafted in Wisconsin. All opinions, as usual, are mine. Thanks for supporting BGSK’s sponsors! See all the Roth recipes here.


Caramelized Onion & Kale Soup au Gratin
Prep time: 
Cook time: 
Total time: 
Serves: 4
  • 1½ tablespoons butter
  • 2 small onions, sliced
  • Salt
  • Olive oil
  • 5 cloves garlic, peeled and left whole
  • 1 head Lacinato kale, stems removed, chopped into bite-sized pieces
  • 4 cups chicken broth, preferably homemade
  • 3 tablespoons white wine
  • 4 slices good bread, toasted
  • 7 ounces aged alpine-style cheese like Roth Grand Cru Reserve
  • 1 scallion, green part only, chopped, for garnish
  1. Caramelize the onions: Set a heavy pan over medium heat. Add the butter and let it melt, then add the onions and cook, stirring very infrequently, until they sizzle and being to soften. Turn the flame to low, and allow the onions to slowly cook, caramelizing as they go. During this time, it is important to make sure the onions are spread as evenly as possible across the pan. Every 10 minutes or so, scrape the bottom and redistribute the onions so each gains the maximum amount of surface area. The intention is to slowly cook the onions so they sweeten in their own juices. If you stir too often, the onions will turn to mush. This process takes about 40 to 50 minutes. At the end, sprinkle the onions with salt. You can do this up to three days ahead of time. If you do, cool to room temp then store in the fridge.
  2. Make the kale: Heat a heavy pot with a lid over medium-high heat. Film the bottom with olive oil, then add 3 garlic cloves and the kale. If there’s water clinging to the kale, that’s good. If not, add a tablespoon of water. Cover the pot to let the kale cook, then uncover and stir every 3 minutes or so, until the kale is wilted. Season with salt. You can make this in advance. If you do, cool to room temperature, then store in the fridge.
  3. Make the soup: combine the caramelized onions, cooked kale, chicken broth, and Chardonnay in a large pot over medium heat. Bring to a simmer, then simmer for 5 minutes to let the flavors combine and the wine cook off. Taste for salt, adding enough to let the flavors pop.
  4. When ready to eat, preheat the oven to broil. Place the crocks in a baking pan that will hold them steady in the oven and ladle the soup into each, leaving about an inch on the top. Put one toast on each crock and then evenly distribute the cheese. Cook until the cheese is melted, just a few minutes–and keep an eye so the cheese doesn’t burn. Serve immediately, garnished with the scallions.


  • caitlin

    Looks delightful.

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