Step 1: Prepare the leeks : Slice the leeks lengthwise and wash thoroughly to remove any dirt between the layers. Slice thinly.

Step 2: Sauté the aromatics : In a large pot, heat butter and olive oil over medium heat. Add chopped onion, garlic, and leeks. Sauté for about 6–8 minutes until softened and fragrant, but not browned.

Step 3: Add potatoes and broth : Add diced potatoes, salt, pepper, and thyme (if using). Stir well. Pour in the broth, bring to a boil, then reduce heat and simmer for 20–25 minutes, until the potatoes are tender.

Step 4: Blend the soup : Once the vegetables are soft, remove from heat. Use an immersion blender (or regular blender) to puree until smooth and creamy. Return the soup to the pot.

Step 5: Add cream and adjust seasoning : Stir in the cream and gently reheat without boiling. Taste and adjust seasoning with salt and pepper.

Step 6: Prepare the crispy shallots : In a small skillet, heat oil over medium heat. Add thinly sliced shallots and fry, stirring frequently, until golden brown and crisp (about 3–5 minutes). Remove with a slotted spoon and drain on paper towels. Sprinkle lightly with salt.

Step 7: Serve : Ladle soup into bowls, drizzle with a bit of cream if desired, and top with crispy shallots and fresh herbs.