Ingredients
For Roasted Garlic
- 1 large whole garlic head
- ½ tablespoon olive oil
For Onion and Leek Base
- 1 tablespoon olive oil
- 9 cups (about 4 large) thinly sliced sweet onions
- 2½ cups (about 2 medium) sliced leeks (light green and white parts only)
- 1 teaspoon salt (divided use)
- 1 teaspoon dried thyme
- 2 tablespoons all-purpose flour
- ⅓ cup dry white wine
- 4 cups vegetable broth
Finishing Ingredients
- 2 cups milk
- Fresh thyme leaves for garnish
- Freshly ground black pepper for garnish
Instructions
- Preheat Oven: Preheat your oven to 350°F (175°C) in preparation for roasting the garlic.
- Roast Garlic: Remove the papery outer skin from the whole garlic head without separating the cloves. Rub ½ tablespoon of olive oil over the garlic head, wrap it tightly in aluminum foil, and bake for 1 hour. After baking, let it cool for 10 minutes, then separate the cloves and peel each one. Set the roasted garlic cloves aside in a small dish.
- Cook Onions and Leeks: While the garlic roasts, heat the remaining 1 tablespoon of olive oil in a large pot over medium heat. Add the thinly sliced onions and leeks, cooking uncovered for 30 minutes while stirring frequently. Then add ½ teaspoon salt and the dried thyme, continuing to cook uncovered for another 30 minutes, stirring occasionally. Add a small amount of water as needed to prevent burning and scrape up any browned bits from the bottom to intensify flavor. The onions should develop a dark golden color.
- Make Roux and Add Liquids: Stir the all-purpose flour into the cooked onion and leek mixture and cook for 1 minute to remove raw flour taste. Pour in the dry white wine and vegetable broth, bringing the soup to a boil. Reduce the heat and let it simmer gently for 30 minutes.
- Blend the Soup: Add the roasted garlic cloves and remaining ½ teaspoon salt to the cooked onion mixture. Transfer this mixture to a blender in batches if necessary and process until completely smooth and creamy.
- Heat and Finish: Return the blended soup to the large pot, add the milk, and gently simmer for 8 minutes to heat through thoroughly. Avoid boiling to prevent milk from curdling. Finally, garnish with fresh thyme leaves and freshly ground black pepper before serving.
Notes
- Be patient while caramelizing onions for the best flavor; the process can take about an hour.
- Use a light or medium-bodied dry white wine for best results, such as Sauvignon Blanc or Pinot Grigio.
- You may substitute milk with a plant-based milk to make this recipe vegan-friendly, though the taste will slightly differ.
- To avoid lumps when adding flour, ensure the onions and leeks are well cooked and evenly coated before stirring in flour.
- If you prefer a thinner soup, add more vegetable broth or milk when reheating.
- The bisque can be made ahead and refrigerated for up to 3 days or frozen for up to 1 month.
- Prep Time: 20 minutes
- Cook Time: 2 hours 48 minutes
- Category: Soup
- Method: Baking
- Cuisine: American
- Diet: Vegetarian