Potato Leek Soup Recipe

Prepare vegetables

Peel and cut potatoes into roughly 1-inch cubes so they cook evenly. Trim root and dark green parts from leeks; halve lengthwise, rinse thoroughly between layers to remove grit, then thinly slice the white and light green parts. Reserve thinly sliced dark green tops for garnish. Dice the onion and carrot (if using). Mince the garlic.

Sweat aromatics

In a large heavy-bottomed pot over medium heat, add butter and olive oil. When the butter foams, add the sliced leeks, diced onion, and carrot. Season lightly with 1/4 tsp of the kosher salt and cook, stirring occasionally, until softened and translucent, about 6–8 minutes. Add the minced garlic and cook 30–60 seconds until fragrant.

Optional roux for slight thickening

If using flour, sprinkle 1 tablespoon of flour over the softened vegetables and stir for 1 minute to cook the raw flour taste; this will help thicken the soup slightly.

Add potatoes and liquid

Add the cubed potatoes to the pot and stir to coat. Pour in the stock, add the bay leaf and thyme sprigs, and bring the mixture to a gentle boil. Reduce heat to maintain a simmer.

Simmer

Simmer until the potatoes are very tender and break apart easily with a spoon, about 15–20 minutes depending on potato size. Skim any foam from the surface if desired.

Remove herbs and blend

Remove and discard the bay leaf and thyme sprigs. For a chunky soup, use a potato masher to mash some of the potatoes in the pot until you reach desired texture. For a smooth soup, use an immersion blender to purée the soup in the pot until silky, or transfer in batches to a countertop blender (cool slightly and fill blender no more than halfway; hold lid with a towel and vent).

Add dairy and adjust texture

Return the soup to low heat if needed. Stir in the milk or half-and-half and warm through gently without boiling to prevent curdling. Taste and adjust seasoning with the remaining kosher salt (about 1–1.25 tsp total) and black pepper. If soup is too thick, add up to 1/2 cup additional stock or water to reach preferred consistency.

Finish with acid and herbs (optional)

If desired, stir in 1–2 teaspoons of lemon juice or a splash of white wine vinegar to brighten flavors. Fold in most of the chopped chives, reserving some for garnish.

Ladle the soup into bowls. Swirl a tablespoon of sour cream or crème fraîche into each bowl if using. Sprinkle with the reserved chopped chives and sautéed or raw thinly sliced leek greens. Drizzle a small amount of olive oil or melted butter, and finish with a pinch of flaky sea salt and a crack of freshly ground black pepper. Serve hot with crusty bread.