Talk about a vegetable that’s everywhere. The humble onion is one of the most common aromatic vegetables, popping up in so many ways across so many cuisines.
And it’s not just for taste. The onion also happens to be a terrifically healthy ingredient. If nothing else, it’s a delicious way to add bulk to a dish without adding many calories or any fat. Thing is, Americans typically use onions in such small quantities that they serve more to highlight the other items in a dish, rather than strut their own stuff.
The exception? A warm and satisfying bowl of onion soup.
There is nothing as soothing as the luscious sweetness of a cooked onion, particularly one from which a caramel color and flavor have been coaxed unhurried over hours. Add a rich broth and a bit of cheese, and you have a delicious luxury.
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The secret is in not rushing the caramelizing of the onions. And that’s a fine way to put your slow cooker to work. It conveniently caramelizes the onions overnight with no effort from you. And my recipe for slow-cooker onion soup walks you through the whole (very easy) thing.
Slow-cooker onion soup
For the onions:
▪ 5 cups sliced yellow onions (about 4 large onions)
▪ 2 shallots, peeled and sliced
▪ 1 clove garlic, minced
▪ 1 tablespoon olive oil
▪ Salt and ground black pepper
For the soup:
▪ 1 teaspoon all-purpose flour
▪ 1/4 cup dry sherry
▪ 1 teaspoon dry thyme
▪ Small sprig fresh rosemary
▪ 1 teaspoon Worcestershire sauce
▪ 2 cups low-sodium chicken broth
▪ 2 cups low-sodium beef broth
▪ 1 cup water
▪ 1 tablespoon lemon juice
▪ 6 thin slices baguette, toasted until golden and quite dry
▪ 1/2 cup grated Gruyere cheese
1. Coat a 4-quart or larger slow cooker with cooking spray. Add onions, shallots, garlic and oil. Toss well, then season with a bit of salt and pepper. Cover and cook on low until the onions are richly colored and sweet, 8 to 10 hours. (The onions at this point can be removed and used for other recipes if you’re not making the soup.)
2. Sprinkle onions with flour and stir until well-combined. Add sherry, thyme, rosemary, Worcestershire sauce, both broths and water, then cover and cook for 4 hours on low or 2 hours on high. Once soup is done, stir in lemon juice and adjust the seasoning.
3. When you’re ready to eat, set the broiler on high. Ladle soup into broiler-safe serving crocks. Top each crock with a thin slice of baguette and a heaping tablespoon of Gruyere. Place the filled crocks on a rimmed baking sheet and broil just until cheese is golden, 1 to 2 minutes. Do not leave the crocks unattended, as they will burn quickly.
Nutrition information per serving: 240 calories, 6 grams fat (2.5 grams saturated), 15 milligrams cholesterol, 34 grams carbohydrates, 3 grams fiber, 8 grams sugar, 10 grams protein, 570 milligrams sodium, 23 percent of calories from fat.