Caramelized Onion and Kale Soup, French Onion-Style

Weekends are a time to put things on the back burner. I mean that literally, of course. It’s a time to slowly melt a great pile of onions to sweet, sticky bliss, bubble a pot of marinara sauce, or make chicken stock for the sake of good cooking sometime else. Sometime less languid than the weekend.

I’ve heard complaints about not getting enough “downtime” these past few holiday party-filled weeks; from Thanksgiving on, it’s a marathon of socializing and getting s%#& done before the real holiday break. And maybe it’s a real marathon here and there. So there may not be a whole lot of time for slowly simmering a soup on the back burner—and that’s too bad. It’s just begun to get cold, here in NYC. The weather has blasted cold winds this week, after taking its time dawdling with winter, playing hooky or hard-to-get. But it’s real now. Soup time—if you can find the time—is here.

Caramelizing onions—like simmering soup itself—is something you just have to sit back and enjoy the slow pace of. I’m sure there are folks offering a hack shortcut to getting similar results. But the weekends are all about taking it slow—you have to just embrace it sometimes. No, this recipe is not great for a weeknight meal but it’s meditative and restorative, hopefully priming you for a busy week ahead.

The French have long appreciated the sweet charms of slow-cooked onions. Naturally, I’d thought of making a French onion soup with this great batch I began to soften in a Dutch oven. But I didn’t want to run out to get beef bones and make beef stock, the traditional broth of soupe a l’oignon. Instead, I had a vat’s worth of turkey broth in my freezer from two recent Thanksgiving birds. Well heck, I thought. Why should there only be one type of soup to make with caramelized onions?

There doesn’t.

There were a few stragglers of kale leaves left in my bunch, getting a little limp in the fridge. Since they would be hopeless as a raw salad that way, and since there were too few of them to make a sautéed side dish with, I decided to add them to this soup. Since it wasn’t going to be proper French onion with turkey stock anyway, might as well keep going with the aberrations. To give it a little more umami and density, I squirted some tomato paste into the pot before adding the stock. Just a smidge here, for a hint.

Then another great question of French onion soups: why is it the only soup we seem to ever serve topped with a crown of crusty bread and melted cheese? This doesn’t make any sense. You could put this atop your tomato soup and pop it in the oven, and not have to serve it with grilled cheese anymore. You could do this to your fill-in-the-blank vegetable, minestrone, chicken soup, or whatever! Or, to your not-so French onion caramelized onion and kale soup, instantly transforming it into something irresistibly soothing. Especially on a cold winter weekend.

Now that the “polar vortex” has gushed its coldest upon NYC, I don’t think we’ll be spending too much time outside. So settle in for a long simmer by the stove, whatever soup you end up with. I’m sure this one isn’t the only solution, but it’s tried, trusted and very good.

Caramelized Onion & Kale Soup, French Onion-Style

(makes about 4 servings)
4 large onions, thinly sliced
2 tablespoons butter
¼ cup cognac or brandy (or substitute with dry white wine)
1 teaspoon tomato paste
6 cups chicken or vegetable stock
6 leaves kale, thick ribs trimmed and torn or sliced into slivers
salt and pepper to taste
4 pieces stale, crusty French bread
about 6 oz Gruyere or Swiss cheese, grated
pinch of herbs de Provence

Melt the butter over low heat in a large, heavy-bottomed pot such as a Dutch oven and add the sliced onions. Add a pinch of salt and cook at very low heat, stirring occasionally, for at least 30 minutes or preferably 1 hour until the onions are completely soft and golden-brown. Be careful to not burn, checking and reducing heat if necessary or stirring more often.

Increase heat to medium and stir in the cognac, brandy or white wine. Let boil and reduce until nearly all evaporated. Stir in the tomato paste thoroughly to combine with the onions and once the pan is getting dry and crackling a bit, pour in all the stock. Stir and bring to a boil. Reduce heat to a low simmer and let cook, covered, for 30 minutes to 1 hour. Add the kale and cook at least another 30 minutes to 1 hour. Taste for seasoning, adding salt and pepper as desired.

Preheat oven to 375 degrees. Ladle the soup into oven-safe individual serving bowls. Place a piece of stale bread in each bowl, and top each one with the grated cheese along with a pinch of the herbs de Provence. Place bowls on a cookie sheet and bake for about 10 minutes, or until the cheese is melted and slightly golden-brown. Serve immediately.

Cost Calculator
(for 4 servings)

4 onions: $1.00
6 leaves kale (at $4/bunch): $1.00

2 tablespoons butter (at $6/lb): $0.38
1 teaspoon tomato paste: $0.20
¼ cup cognac: $1.00
6 cups homemade turkey stock: $2.00
4 pieces stale French bread: $1.00
6 oz grated cheese: $2.00
salt, pepper, pinch of herbs de Provence: $0.20

Total: $8.78

Health Factor

Five brownie points: Adding kale to this soup not only saves your kitchen from random leafy green scraps but adds welcome vitamins to a once-classic soup. With it, you’ll get some Vitamin K and antioxidants to go along with your oniony soup (and proteins and calcium if using homemade stock made from bones). But it’s easy to make a vegetarian version of this with vegetable stock, too. Naturally, adding cheese to melt on top will add richness and cholesterol, but it’s a light touch that can elevate this soup to a satisfying meal.

Green Factor

Seven maple leaves: A soup is a great repository for leftover scraps. Working with a flavorful base of caramelized onions, you could add pretty much anything else to it you like—like those wilting kale leaves, or fill-in-the-blank leafy green. Broths too are great for using up bones and carcasses like from your roasted poultry entrée. Finally, this soup happens to be a great way of using up leftover French bread, too—which, when fully absorbed, becomes spongelike, almost the texture of custard.