Caramelized Onion and Fennel Soup with Thyme
A fragrant, slow-simmered soup featuring tender caramelized onions and sweet fennel, accented by fresh thyme for depth. This french-inspired soups (vegetarian) ready in about 85 minutes pairs large (about 2 lbs) yellow onions, medium fennel bulb, unsalted butter for a weeknight-friendly dinner that comes together with one pan and minimal cleanup. Each serving lands at about 120 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. 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 (about 2 lbs) yellow onions
- 1 medium fennel bulb
- 3 tbsp unsalted butter
- 2 tbsp olive oil
- 3 sprigs fresh thyme sprigs
- 6 cups vegetable broth
- 2 tsp salt
- 1 tsp black pepper
- 1 leaf bay leaf
Instructions
- Step 1: Thinly slice 4 large yellow onions and 1 medium fennel bulb into 1/8-inch strips. Heat 3 tbsp unsalted butter and 2 tbsp olive oil in a large pot over medium heat.
- Step 2: Add the sliced onions and fennel along with 3 sprigs fresh thyme and 1 bay leaf. Cook gently, stirring occasionally, for 45 minutes until the vegetables are deeply golden and caramelized.
- Step 3: Pour in 6 cups vegetable broth, season with 2 tsp salt and 1 tsp black pepper, and bring to a simmer. Cook uncovered for 20 minutes to meld flavors.
- Step 4: Remove thyme sprigs and bay leaf, then use an immersion blender to puree the soup until smooth but still slightly textured.
- Step 5: Serve hot, garnished with a fresh thyme sprig if desired.
Equipment for this recipe
Top-rated tools to make this recipe successfully.
Frequently asked questions
How long does Caramelized Onion and Fennel Soup with Thyme take to make?
Total time is about 85 minutes (15 min prep + 70 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 Caramelized Onion and Fennel Soup with Thyme?
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 medium fennel bulb from drying out.
Can I substitute ingredients in Caramelized Onion and Fennel Soup with Thyme?
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 Caramelized Onion and Fennel Soup with Thyme 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 Caramelized Onion and Fennel Soup with Thyme 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.
