Slow-Simmered Caramelized Onion Soup
A deeply sweet and savory soup made with onions cooked low and slow until golden brown, finished with a touch of thyme and crusty bread. This french-inspired soups (vegetarian) ready in about 85 minutes pairs thinly sliced 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 310 calories and feeds 6, 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.
Ingredients
- 1 lb, thinly sliced yellow onions
- 3 tbsp unsalted butter
- 1 tbsp all-purpose flour
- 3 cups chicken stock
- 1 tsp, chopped fresh thyme
- 4, toasted baguette slices
Instructions
- Step 1: Melt 3 tbsp unsalted butter in a large Dutch oven over medium-low heat, then add 1 lb thinly sliced yellow onions, stirring to coat.
- Step 2: Cook onions for 45 minutes, stirring every 5 minutes, until deeply caramelized and golden brown, reducing heat if browning too quickly.
- Step 3: Sprinkle 1 tbsp all-purpose flour over onions and stir for 1 minute to cook off raw flour taste.
- Step 4: Gradually whisk in 3 cups chicken stock, bring to a gentle simmer, then stir in 1 tsp chopped fresh thyme and cook uncovered for 15 minutes.
- Step 5: Ladle soup into bowls over toasted baguette slices, garnishing with extra thyme if desired.
Frequently asked questions
How long does Slow-Simmered Caramelized Onion Soup take to make?
Total time is about 85 minutes (20 min prep + 65 min cook). Most home cooks find this fits comfortably into a weeknight; double the batch on Sunday for two dinners.
How do I store leftover Slow-Simmered Caramelized Onion Soup?
Cool to room temperature within 2 hours, then store in an airtight container in the fridge for up to 4 days. Reheat covered in a 350°F oven for 10-12 minutes, or microwave at 70% power in 60-second bursts to keep thinly sliced yellow onions from drying out.
Can I substitute ingredients in Slow-Simmered Caramelized Onion Soup?
Yes — most ingredients in this recipe have flexible swaps. For oil, use any neutral high-smoke-point oil (avocado, grapeseed, refined coconut). For aromatics, dried herbs at ⅓ the volume of fresh work in a pinch. The full ingredient list is shoppable on Instacart so you can see substitutes in real time.
How do I scale Slow-Simmered Caramelized Onion Soup for a different number of people?
The recipe is written for 6 servings. Multiply each ingredient by (your serving target / 6). Cook time stays roughly the same up to 2x; for 3-4x batches, switch from a skillet to a sheet pan or stockpot so the food isn't crowded — overcrowding steams instead of browns.
Is Slow-Simmered Caramelized Onion Soup vegetarian?
Yes — this recipe is tagged vegetarian based on its ingredient list. Always cross-check labels for packaged ingredients (sauces, broths, condiments) since formulations vary by brand.
What others are saying
- ★★★★★
My family loved this soup. It was so comforting and the flavors were amazing.
- ★★★★★
A new favorite in my kitchen. The slow simmer really brings out the sweetness of the onions.
- ★★★★★
This soup is absolutely divine! The caramelized onions are perfect, and it's the best soup I've ever made.
