Roasted Garlic Onion Soup (Printable)

Comforting soup with slow-roasted garlic, caramelized onions, and crispy herb croutons.

# What You’ll Need:

→ Vegetables

01 - 3 large yellow onions, thinly sliced
02 - 2 whole heads garlic
03 - 1 large leek, white and light green parts, sliced
04 - 1 celery stalk, diced
05 - 1 medium carrot, diced

→ Fats

06 - 2 tablespoons olive oil
07 - 2 tablespoons unsalted butter

→ Liquids

08 - 1/2 cup dry white wine
09 - 5 cups vegetable broth
10 - 1 teaspoon soy sauce, optional

→ Herbs and Seasonings

11 - 2 sprigs fresh thyme
12 - 1 bay leaf
13 - 1/2 teaspoon dried oregano
14 - Salt and black pepper to taste

→ Herb Croutons

15 - 3 cups day-old baguette, cut into 3/4-inch cubes
16 - 2 tablespoons olive oil
17 - 1 tablespoon fresh parsley, chopped
18 - 1 teaspoon dried thyme or Italian herbs
19 - 1/4 teaspoon garlic powder
20 - Pinch of salt

# Steps:

01 - Preheat oven to 400°F. Slice the tops off garlic heads, drizzle with 1 tablespoon olive oil, wrap in foil, and roast for 40 minutes until soft and golden. Remove from oven, let cool, then squeeze roasted garlic from skins and set aside.
02 - While garlic roasts, heat 1 tablespoon olive oil and butter in a large pot over medium-low heat. Add onions, leek, celery, and carrot. Cook, stirring frequently, until onions are deeply caramelized and golden brown, approximately 25 to 30 minutes.
03 - Deglaze the pot with white wine, scraping up browned bits from the bottom. Simmer until liquid is reduced by half.
04 - Stir in the roasted garlic, vegetable broth, soy sauce if using, thyme sprigs, bay leaf, and oregano. Bring to a boil, then reduce heat and simmer uncovered for 25 minutes. Remove thyme sprigs and bay leaf.
05 - Toss bread cubes with olive oil, herbs, garlic powder, and salt. Spread on a baking sheet and bake at 400°F for 10 to 12 minutes, turning once, until golden and crisp.
06 - Taste soup and adjust seasoning with salt and pepper as needed. For a smoother texture, blend part or all of the soup using an immersion blender.
07 - Ladle soup into bowls and top with a generous handful of herb croutons. Garnish with fresh parsley if desired.

# Expert Advice:

01 -
  • The roasted garlic becomes sweet and spreadable, nothing like raw garlic's bite.
  • Those caramelized onions do most of the flavor work, so the soup tastes like you spent hours fussing when you really didn't.
  • Herb croutons make it feel fancy without requiring any special skills.
02 -
  • Don't skip the low-and-slow caramelization of onions—turning up the heat to speed things along gives you brown onions, not caramelized ones, and the soup suffers for it.
  • Roasted garlic completely transforms this soup; regular garlic won't deliver the same sweet, mellow quality that makes people ask for the recipe.
03 -
  • A tiny splash of soy sauce adds umami depth without making the soup taste salty or Asian—most people won't know it's there, but they'll notice something makes it taste more fully itself.
  • For a creamier version, stir in a splash of heavy cream or crème fraîche just before serving, or float a spoonful of gruyère on top for that classic French bistro finish.
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