Slow-Simmered French Onion Soup

By AislePrompt Editorial · Published 2026-04-22 · Updated 2026-04-22

A classic French comfort food featuring deeply caramelized onions simmered in rich broth, topped with a golden crust of melted Gruyère cheese. This French soup recipe, ready in about 90 minutes, pairs yellow onion, unsalted butter, and all-purpose flour for a weeknight-friendly dinner that comes together with one pan and minimal cleanup. Each serving lands at about 350 calories and feeds 4, so it slots cleanly into a weekly meal plan and pairs well with a quick salad or grain on the side. Tap "Build a week of meals around this recipe" below to drop this recipe into your week and send the ingredients straight to Instacart. Nutrition values are approximate, calculated from USDA FoodData Central (fdc.nal.usda.gov) — verify against ingredient labels for any health-driven dietary plan.

Ingredients

• 700 grams yellow onion
• 2 tablespoons unsalted butter
• 1 tablespoon all-purpose flour
• 4 cups beef broth
• 120 milliliters dry white wine
• 50 grams Gruyère cheese
• 4 slices baguette

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Instructions

1. Step 1: Thinly slice 700 grams yellow onions and cook in 2 tablespoons unsalted butter over medium-low heat for 45-50 minutes until deeply golden brown, stirring occasionally to prevent burning.
2. Step 2: Sprinkle 1 tablespoon all-purpose flour over onions, stir to coat, and cook for 1 minute.
3. Step 3: Pour in 120 milliliters dry white wine, simmer for 5 minutes to evaporate alcohol, then add 4 cups beef broth and simmer uncovered for 20 minutes.
4. Step 4: Ladle soup into oven-safe bowls, top each with 50 grams grated Gruyère cheese, and broil under high heat for 2-3 minutes until golden.