Ingredients
Method
- Prepare the leeks. Trim off the dark green tops and root ends. Slice the white and light green parts in half lengthwise, then slice into thin half-moons. Place in a large bowl of cold water and swish around to remove any dirt or sand trapped between the layers. Lift the leeks out of the water and drain well. Pat dry.Cook the leeks. Melt butter in a large heavy-bottomed pot or Dutch oven over medium-low heat. Add the leeks and 2 teaspoons kosher salt. Stir to coat the leeks in butter. Reduce heat to low and cook, stirring occasionally, until the leeks are very soft, sweet, and translucent, about 15-20 minutes. Do not let them brown—if they start to color, reduce the heat. The goal is to sweat them gently until they're tender and sweet.Add potatoes and stock. Add the diced potatoes to the pot and stir to combine. Pour in enough chicken stock to just cover the potatoes, about 3-4 cups. Bring to a simmer over medium heat, then reduce heat to low and simmer gently until the potatoes are completely tender and falling apart, about 20-25 minutes. Test with a fork—they should be very soft.Puree the soup. Remove from heat. Use an immersion blender to puree the soup until completely smooth and silky. If you don't have an immersion blender, carefully transfer the soup in batches to a regular blender and puree until smooth. Return the soup to the pot.Finish with cream. Stir in the heavy cream and crème fraîche. Warm gently over low heat until heated through. Do not boil. Taste and adjust seasoning with more salt if needed. Add a pinch of cayenne pepper for subtle heat.Adjust consistency. If the soup is too thick, thin with additional stock or cream until it reaches your desired consistency. It should be creamy and pourable but not watery.Serve hot or cold. For hot soup, ladle into bowls and garnish with a dollop of crème fraîche and sliced fresh chives. For cold Vichyssoise, let the soup cool to room temperature, then refrigerate until completely chilled, at least 4 hours or overnight. Serve cold with the same garnishes.
Notes
Yukon Gold Potatoes: Yukon Gold potatoes are the best choice for this soup. They have a naturally buttery flavor and creamy texture when pureed. They're also less starchy than Russets, so they won't get gluey or gummy when blended. Peel the potatoes for a silky-smooth, elegant soup. Leaving the skins on creates flecks in the puree and a more rustic texture—fine for casual family meals, but not ideal for tasting menus or elegant presentations.
Russet Potatoes: Russets work but are riskier. They're high in starch, which makes them very smooth when pureed but also prone to becoming gluey if overworked. If using Russets, blend gently and don't overprocess. Always peel Russets—the skins are thick and tough and won't break down well.
Leek Preparation is Critical: Leeks trap dirt and sand between their layers. Always slice them first, then wash thoroughly in a bowl of cold water. Lift them out of the water (don't pour the water out—the dirt will settle at the bottom and you'll pour it back over the leeks). Drain well and pat dry before cooking. Gritty soup is ruined soup.
Cooking the Leeks Low and Slow: This is the most important step. The leeks must cook gently over low heat until they're completely soft, sweet, and translucent—no browning, no color. This takes 15-20 minutes. If you rush it and cook them over high heat, they'll brown and develop a sharp, bitter flavor instead of sweetness. Low and slow is the key.
Stock Amount May Vary: The amount of stock you need depends on the size of your leeks and potatoes. Start with 3 cups and add more as needed to just cover the potatoes. It's easier to add stock than to reduce it, so go conservatively. After pureeing, you can always thin the soup with more stock or cream to reach your desired consistency.
Immersion Blender vs Regular Blender: An immersion blender is easier and faster—you can puree the soup right in the pot. A regular blender gives you a slightly smoother texture but requires transferring hot soup in batches, which is messier and more dangerous. If using a regular blender, fill it only halfway, hold the lid down with a towel, and start on low speed to prevent hot soup from exploding out the top.
Crème Fraîche: Crème fraîche adds tangy richness that balances the sweetness of the leeks. If you don't have crème fraîche, substitute sour cream or additional heavy cream. The soup will still be good but won't have quite the same depth. You can make homemade crème fraîche easily (cream + buttermilk, cultured overnight).
Heavy Cream: Heavy cream is essential for the silky texture and richness. Don't substitute milk or half-and-half—the soup will be thin and lack body. If you want a lighter version, skip the heavy cream and use only crème fraîche, but the texture won't be as luxurious.
Cayenne Pepper: Just a pinch. You shouldn't taste heat—it's there to brighten the flavors and add subtle warmth. If you can taste it, you've added too much.
Serving Hot (Potage Parmentier): Reheat gently over low heat. Do not boil or the cream may separate. Ladle into bowls and garnish with a dollop of crème fraîche, sliced chives, and optionally a drizzle of herb oil or crispy leek rings for texture.
Serving Cold (Vichyssoise): Let the soup cool completely to room temperature, then refrigerate until thoroughly chilled, at least 4 hours or overnight. The soup will thicken as it chills. If it's too thick, thin with a little cold stock or cream before serving. Taste and adjust seasoning—cold dulls flavors, so you may need to add more salt. Serve in chilled bowls with the same garnishes.
Make Ahead: This soup actually improves overnight as the flavors meld. Make it a day ahead, store in the refrigerator, and reheat gently (for hot) or serve cold (for Vichyssoise). It keeps refrigerated for up to 5 days. Reheat gently and whisk in a splash of cream if it's too thick.
Freezing: Potato leek soup freezes well. Cool completely, then freeze in airtight containers for up to 3 months. Thaw overnight in the refrigerator and reheat gently, whisking in a little cream to restore the texture. The texture may be slightly grainy after freezing but will still taste good.
Garnish Options:
- Sliced fresh chives (classic)
- Dollop of crème fraîche
- Drizzle of herb oil (parsley or chive oil)
- Crispy leek rings (thinly sliced leeks fried until golden)
- Crispy bacon or pancetta bits (for a heartier version)
- Croutons