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.
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.
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