Prep the leeks: Slice off the dark green tops and root ends. Split the leeks lengthwise, then rinse thoroughly between the layers to remove grit. Slice into thin half-moons.

Prep the potatoes: Peel if you like a smoother soup, or leave skins on for a rustic version. Cut into 1-inch chunks for even cooking.

Sweat the aromatics: In a large pot, warm the butter or olive oil over medium heat. Add leeks with a pinch of salt. Cook 7–10 minutes, stirring occasionally, until soft and sweet but not browned. Add garlic and cook 30 seconds until fragrant.

Build the base: Add potatoes, thyme, bay leaf, and stock. The liquid should just cover the vegetables. Bring to a gentle boil, then reduce to a simmer.

Simmer: Cook 15–20 minutes, until the potatoes are very tender and easily pierced with a fork.

Remove aromatics: Fish out the bay leaf and any woody thyme stems. Taste the broth and adjust salt if needed.

Blend to your preferred texture: For silky soup, use an immersion blender right in the pot. For a chunkier finish, blend only half the soup and return it to the pot, or lightly mash with a potato masher.

Add cream (optional): Stir in heavy cream or half-and-half. Warm gently over low heat. Do not boil after adding dairy.

Season and brighten: Add black pepper to taste. If the flavor needs lift, add a small squeeze of lemon. Taste and adjust salt again.

Serve: Ladle into bowls. Top with a drizzle of olive oil or a pat of butter, chopped chives or scallions, and extra pepper if you like. Crusty bread is a great side.