Slow-Caramelized French Onion Soup with Crispy Baguette

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

A deeply aromatic soup where onions caramelize slowly for 45 minutes, layered with a toasted baguette slice and Gruyère cheese melted to golden perfection. This French-inspired soup recipe, ready in about 95 minutes, pairs yellow onions, unsalted butter, all-purpose flour for a weeknight-friendly dinner that comes together with one pan and minimal cleanup. Each serving lands at about 420 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 "Plan a meal with the AI" 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

• 4 large, thinly sliced yellow onions
• 3 tbsp unsalted butter
• 1 tbsp all-purpose flour
• 1/2 cup dry white wine
• 2 cups beef stock
• 1 slice, 1/2-inch thick baguette
• 1/4 cup grated Gruyère cheese
• 1 tsp chopped fresh thyme
• 1/2 tsp salt
• 1/4 tsp black pepper

The stock pot we’d simmer this in → Best Stock Pots for 2026: Top Picks + Buying Guide

Instructions

1. Step 1: In a large Dutch oven over medium-low heat, melt 2 tbsp butter. Add all sliced onions and cook uncovered for 45 minutes, stirring every 10 minutes with a wooden spoon until deeply golden brown and caramelized—do not rush this step.
2. Step 2: Stir in remaining 1 tbsp butter, then immediately add flour and cook for 1 minute until golden, stirring constantly to avoid burning.
3. Step 3: Pour in wine, scraping up all browned bits from the pot, and simmer for 5 minutes until liquid reduces by half and is fragrant.
4. Step 4: Add 2 cups beef stock, 1 tsp thyme, salt, and pepper. Bring to a gentle simmer, then reduce heat to low and cook uncovered for 20 minutes to meld flavors, stirring occasionally until the liquid is slightly thickened.
5. Step 5: Preheat broiler. Place baguette slice on a baking sheet, top with 1/4 cup grated Gruyère, and broil 3-4 inches from heat for 2-3 minutes until cheese is bubbly and golden.
6. Step 6: Ladle soup into bowls, top with the broiled baguette slice, and serve immediately.