Roasted Garlic Onion Soup (Printable)

Slow-roasted garlic and caramelized onions blend with crispy herb croutons in this flavorful soup.

# Required Ingredients:

→ 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 & Oils

06 - 4 tablespoons olive oil, divided
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 & 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 herb seasoning
19 - 1/4 teaspoon garlic powder
20 - Pinch of salt

# Preparation Steps:

01 - Preheat oven to 400°F. Slice tops off garlic heads, drizzle with 1 tablespoon olive oil, wrap in foil, and roast for 40 minutes until soft and golden. Cool completely, then squeeze roasted garlic from skins and set aside.
02 - While garlic roasts, heat 1 tablespoon olive oil and butter in large soup pot over medium-low heat. Add onions, leek, celery, and carrot. Cook, stirring frequently, for 25 to 30 minutes until onions are deeply caramelized and golden brown.
03 - Pour dry white wine into pot, scraping up all browned bits from bottom. Simmer until liquid reduces by half, approximately 5 minutes.
04 - Stir in roasted garlic, vegetable broth, soy sauce if using, thyme sprigs, bay leaf, and oregano. Bring to boil, then reduce heat and simmer uncovered for 25 minutes. Remove thyme sprigs and bay leaf.
05 - Toss bread cubes with 2 tablespoons olive oil, parsley, thyme or Italian herbs, garlic powder, and pinch of salt. Spread on baking sheet and bake at 400°F for 10 to 12 minutes, stirring once halfway through, until golden and crisp.
06 - Taste soup and adjust seasoning with salt and pepper as needed. For smoother texture, partially or fully blend with immersion blender if desired.
07 - Ladle soup into bowls and top generously with herb croutons. Garnish with fresh parsley if desired.

# Expert Suggestions:

01 -
  • The roasted garlic loses its sharp edge and becomes buttery and mild, making this soup approachable even for garlic skeptics.
  • It's a one-pot wonder that feels fancy enough to serve guests but easy enough for a quiet weeknight dinner.
  • Those herb croutons add a textural contrast that transforms the whole eating experience.
02 -
  • The low-and-slow caramelization of onions cannot be rushed—those thirty minutes of stirring are what separates a good soup from one that tastes genuinely homemade and profound.
  • Day-old bread is essential for croutons because fresh bread will absorb oil and become soggy instead of crispy, so plan accordingly or buy a baguette the day before.
03 -
  • Make this soup a day ahead and refrigerate it—the flavors deepen overnight and it reheats beautifully, though you'll want to make fresh croutons to keep them crispy.
  • If your bread cubes are perfectly fresh, dry them in a low oven for ten minutes before tossing with oil to help them crisp up better.
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