French Onion White Bean Soup

A Hearty Vegetarian Comfort Dish with Crispy Gruyère Croutons

Time Overview

  • Prep Time: 15 minutes

  • Cook Time: 35 minutes

  • Total Time: 50 minutes

Ingredients

For the Soup

  • 2 tablespoons salted or unsalted butter

  • 4 medium yellow onions (about 2 pounds), thinly sliced (uniform slicing ensures even caramelization)

  • 1 teaspoon dried thyme leaves (or 4–5 fresh thyme sprigs, leaves removed)

  • 1 teaspoon sugar (optional, omit for low-sugar diets; see Notes)

  • 1 teaspoon salt (adjust to taste)

  • Freshly ground black pepper

  • 1 tablespoon balsamic vinegar

  • 1 tablespoon soy sauce or tamari (low-sodium preferred)

  • 4 cups vegetable stock (low-sodium recommended)

  • 2 (14-ounce) cans white beans (e.g., cannellini or butter beans), drained and rinsed (reduces excess sodium)

For the Gruyère Croutons

  • 2 tablespoons salted or unsalted butter, melted

  • 1 teaspoon Dijon or whole-grain mustard

  • 1 teaspoon dried thyme leaves (or 4–5 fresh thyme sprigs, leaves removed)

  • ½ pound bread (sourdough or ciabatta recommended), cut into 1-inch cubes

  • 3 ounces Gruyère cheese, finely grated

  • Salt and freshly ground black pepper (to taste)

Preparation Steps

1. Caramelize the Onions (Soup Base)

  • Heat a large pot or Dutch oven over medium-high heat. Add butter and melt until foaming.

  • Add sliced onions, thyme, sugar, and salt. Stir to coat onions evenly with butter.

  • Reduce heat to medium (if onions brown too quickly) and cover. Simmer for 20 minutes, stirring every 2–3 minutes. Onions should become deep golden-brown and tender.

  • Note: Avoid overcrowding the pot; a larger vessel ensures even heat distribution for uniform caramelization.

2. Make the Gruyère Croutons

  • Preheat oven to 350°F (175°C) and line a baking sheet with parchment paper.

  • In a large bowl, melt butter (microwave 30–45 seconds or over low heat). Add mustard, thyme, salt, and pepper; whisk to combine.

  • Toss bread cubes in the butter mixture until fully coated. Spread on the prepared baking sheet in a single layer (no overlapping).

  • Sprinkle Gruyère evenly over the bread, then bake 16–18 minutes until golden and crisp. Cool slightly (croutons crisp further as they cool).

3. Simmer the Soup

  • Uncover the onions and add balsamic vinegar and soy sauce. Stir vigorously to deglaze the pot, scraping up browned bits (critical for flavor).

  • Add vegetable stock and drained beans. Stir, then cover and simmer on medium heat for 10 minutes.

  • Season with additional salt and black pepper to taste (generous pepper enhances depth).

4. Serve

  • Ladle soup into deep bowls. Top with a portion of Gruyère croutons and a sprinkle of fresh thyme leaves for garnish.

Notes & Adaptations

  • Low-Sodium Variation: Use low-sodium stock, unsalted butter, and tamari. Omit sugar (or use ½ teaspoon) and increase balsamic vinegar for sweetness.

  • Umami Boost: Add 1 tablespoon dry white wine during deglazing or double balsamic/soy sauce for richer flavor.

  • Texture Enhancements: Add diced potato (½ pound) with the beans for thickness, or wilt kale/spinach during the final 2 minutes of cooking.

  • Storage: Soup improves after 24 hours in the fridge; croutons stay crisp for 3 days (refresh in a 350°F oven for 5 minutes).

Recipe adapted from user feedback and traditional techniques for optimal flavor and texture.