Creamy Potato Leek Soup

Wash the leeks like they are hiding sand, because they are

Leeks grow in layers and trap grit. Slice the white and pale green part, soak the slices in cold water, lift them out, and do it again if the bowl is gritty. The dark green tops are tougher. You can simmer a few in the pot and strain them out, or compost them. Do not serve a spoonful of sand and call it rustic.

Butter and oil, then the leeks, eight to ten minutes until they are soft and sweet. Garlic and thyme for a minute. Potatoes and broth, simmer until the potatoes crush easily. Blend until smooth. Stir in milk or cream. Salt and white pepper. Chives if you have them.

A blender full of hot soup needs a vented lid and a towel over the top. Fill it halfway. An immersion blender in the pot is calmer. Either way, the soup has to be smooth on purpose. Lumps of undercooked potato mean it needed more simmer, not more blending of raw cubes.

Cream is optional richness, and the soup is still perishable

A cup of milk or cream makes the pot taste like a bistro and makes it a dairy dish. Skip it and you have a potato-leek broth that is lighter and still good. Anyone who avoids milk needs that version, and they need a broth that is not "cream style" from a carton. Read labels.

USDA FSIS wants the refrigerator at 40°F or below and leftovers chilled within two hours, one hour above 90°F, in shallow containers. Soups keep three to four days in the fridge on their chart, and about two to three months in the freezer for quality. Potato soups get grainy after freezing. That is quality. Safety at a steady 0°F holds longer. Reheat to a boil and stir. A skin on the surface of refrigerated soup is starch and protein, not automatically mold. Mold is fuzzy or colored in a way a spoon-stir will not fix. Discard moldy soup. Stir a skin back in if the soup still smells like potatoes and leeks.

The card's cost is a planning figure. Leeks can be pricey compared with onions. An onion will make a different, sharper soup. Do not call it the same. See the content disclaimer.

Vichyssoise is the cold version, with the same rules

Chilling this soup and serving it cold is a classic move. The soup still had to be cooked, cooled fast, and held at 40°F. A pot that cooled on the counter all night and is now "cold soup" is a bad pot. Discard it. Cold soup sits out at a picnic on the same clock as any other perishable food. Keep the bowl nested in ice if it will sit, and discard it after the two-hour mark, one hour in hot weather.

Potatoes

Peeled cubes cook more evenly in a puree. Unpeeled potatoes can be used if you washed them and you want the skins blended in. Green skin and green flesh should be cut away deeply or the potato discarded. This page will not invent a dose for the bitter compounds in green potato. The practical instruction is: do not cook green potatoes into a family soup.

A potato that is sprouted but still firm can be peeled deeply. A potato that is soft, wet, or moldy is trash. Sprouts are not a reason to keep a rotten potato.

Thyme, pepper, and salt

Dried thyme that smells like hay from a distant year should be omitted. White pepper is a look, so the soup stays pale. Black pepper works and shows. Salt late, because broth is often salty and potatoes drink it. The Dietary Guidelines for Americans, 2020 to 2025, say to limit sodium. A salted broth plus a heavy hand plus cheese on the side is three salts. Pick one place to season.

Six servings from four large potatoes is a modest bowl. A huge bowl is two servings. The math on the card only works if you serve the amount you divided. Eating half the pot is fine. It is not one serving.

Further reading: USDA FSIS refrigeration and leftover charts; Dietary Guidelines for Americans, 2020 to 2025.

Leeks, twice in the water

The first soak loosens the obvious grit. The second soak is for the grit you did not believe was there. Lift the slices out with your hands or a spider. Pouring the bowl through a strainer pours the sand back onto the leeks. That is the mistake. A gritty soup cannot be blended into smoothness. The sand stays. If you discover grit after cooking, the pot is unpleasant and you cannot filter it easily. Start the soak over on the next bunch rather than hoping.

Cook the leeks until they are sweet and soft, longer than an onion if the pieces are thick. A pale, crunchy leek makes a soup that tastes like raw onion water no matter how long the potato simmers. Garlic and thyme are brief. Thyme stems can go in and come out if you used a sprig. Dried thyme stays in. Use less dried than fresh.

Potatoes and the blender

Cubes of a similar size so the pot finishes together. A huge chunk and a small dice means you either overcook the dice into nothing or leave the chunk raw. Raw potato does not blend into a silky soup. It blends into a grainy, starchy soup with hard bits. Simmer until a cube breaks with a spoon, then blend.

Milk or cream goes in after the blend, off a hard boil, so it does not scorch on the bottom or separate into flecks. Stir. Taste. Potatoes eat salt. A pot that tasted salty before the potatoes were in can taste flat after. Add salt in pinches. White pepper disappears. Black pepper looks like specks. Either is fine. Chives, if they are fresh, go on the bowl. A slimy bunch of chives from the drawer does not. Skip them.

Cold soup only if the chill was deliberate

If you want it cold, chill it in the refrigerator in shallow containers, not in the cooking pot on the porch. Stir before you serve, because the starch settles. A cold bowl needs a little more salt than a hot one, because cold dulls seasoning. Taste it cold before you decide it is underseasoned and dump in a spoon of salt you cannot take back. A swirl of something dairy on top is optional and should be kept cold too. A picnic table in July is a short window. Eat it, or put it back on ice. Do not leave a tureen out while the afternoon happens.