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The first really cold night of October my mother made a big pot of potato soup, and the kitchen windows fogged up before my father got home from work. She never stirred a spoon of flour into hers. She said a potato soup thickened with flour was a potato soup that didn’t trust its own potatoes, and she had a point, because hers was thicker and creamier than any I have eaten since.
Here is how it works. Russet potatoes are full of starch. Simmer them in broth until they fall apart, add the milk, then push a potato masher down into the pot a few times. About a third of the potatoes break down into the broth and turn it velvety, and the rest stay in tender chunks. The choice of potato matters more than anything else in the recipe, so that is explained first below. On top, a handful of sharp cheddar that melts in the bowl, sliced green onion and plenty of black pepper. My brothers crumbled crackers into theirs until it was nearly solid.
Why this potato soup works
- Russets, or half russets and half Yukon Gold. Russets are starchy and break down into the broth to thicken it. Yukon Golds hold their shape and give buttery chunks. Waxy red potatoes stay firm and will not thicken the soup.
- Mashed in the pot. A few pushes of the masher release the starch. That is the thickener, no flour needed.
- Milk added at the end, never boiled hard. A gentle simmer keeps the soup smooth. A hard boil can make it grainy.
- Onion and celery softened in butter first. They give the soup its sweet, savory base.
Ingredients
Makes about 10 cups, 6 generous bowls. The measurements are in US cups with grams in brackets.
For the soup
- 4 tablespoons unsalted butter (56g)
- 1 medium yellow onion, finely chopped (about 1 1/2 cups, 160g)
- 2 celery ribs, finely chopped (about 3/4 cup, 90g)
- 3 pounds russet potatoes (1.35kg), peeled and cut into 3/4 inch cubes
- 4 cups chicken or vegetable broth (950ml)
- 1 1/2 teaspoons fine salt, plus more to taste
- 1/2 teaspoon freshly ground black pepper, plus more to serve
- 2 cups whole milk (475ml)
- 1/2 cup heavy cream (120ml), optional
To serve
- 1 cup shredded sharp cheddar cheese (115g)
- 3 green onions, thinly sliced
- Saltine crackers or crusty bread
For the creamiest soup with the most body, use all russets. For more distinct chunks, use half russets and half Yukon Gold. Avoid red or other waxy potatoes.
How to make potato soup
- Melt the butter in a large heavy pot over medium heat. Add the onion and celery and cook gently, stirring now and then, for 8 to 10 minutes, until soft and sweet but not browned.
- Add the potatoes, broth, salt and pepper. Bring to a boil, then lower the heat, cover partly and simmer for 15 to 20 minutes, until the potatoes fall apart when pressed with a spoon.
- Pour in the milk, and the cream if using. Heat gently until steaming, without letting it boil hard.
- Push a potato masher straight down into the pot 8 to 10 times, around the pot, mashing about a third of the potatoes into the broth and leaving the rest in chunks.
- Simmer gently for 5 more minutes, stirring, until thick and creamy. If it gets too thick, add a splash of milk. Taste and add salt.
- Ladle into bowls and top each with cheddar, green onion and black pepper. Serve with crackers.
Tips that make the difference
- Cut the potatoes the same size so they cook through at the same time.
- Stop mashing early. You can always mash more; you cannot put the chunks back.
- Stir from the bottom once the milk is in. Potato starch can catch on the pot.
- The soup thickens a lot as it stands. Thin leftovers with milk when you reheat them.
Variations
- Cheesy. Stir 1 cup (115g) shredded cheddar into the pot at the end, off the heat, until melted.
- Loaded with vegetables. Add a diced carrot with the onion and a cup of frozen corn with the milk.
- Lighter. Skip the cream and use 2 1/2 cups of milk.
- Chicken. Stir in 2 cups of shredded cooked chicken with the milk for a heartier supper.
Storage and make-ahead
Cool the soup and refrigerate in a covered container for up to 4 days.
It sets thick in the refrigerator. Reheat gently over low heat with a splash of milk, stirring, and never let it boil hard.
Potato soup with milk can turn grainy in the freezer. If you want to freeze it, freeze it before adding the milk for up to 2 months, then thaw, reheat and add the milk.
Frequently asked questions
Which potatoes are best for potato soup?
Russets, for the most body, because their starch thickens the broth. Half russets and half Yukon Golds gives creamy soup with chunks that hold their shape. Red potatoes will not thicken it.
How do I thicken potato soup without flour?
Mash about a third of the cooked potatoes right in the pot. The starch they release thickens the soup.
Why did my potato soup turn grainy?
It boiled hard after the milk went in. Keep it at a gentle simmer.
Can I make it in a slow cooker?
Yes. Cook the softened onion and celery, potatoes and broth on low for 6 to 7 hours, then add the milk, mash and heat through for 20 minutes.
Trust the potatoes. They will thicken it themselves, the way they always did on the first cold night of October.
Old-Fashioned Potato Soup (Thickened With Potatoes, Not Flour)
Old-fashioned creamy potato soup with no flour: onion and celery softened in butter, russet potatoes simmered in broth, milk added, and a third of the potatoes mashed right in the pot. Cheddar and green onion on top.
Ingredients
- 4 tablespoons unsalted butter
- 1 medium yellow onion, finely chopped
- 2 celery ribs, finely chopped
- 3 pounds russet potatoes (1.35kg), peeled and cut into 3/4 inch cubes
- 4 cups chicken or vegetable broth
- 1 1/2 teaspoons fine salt, plus more to taste
- 1/2 teaspoon freshly ground black pepper, plus more to serve
- 2 cups whole milk
- 1/2 cup heavy cream (120ml), optional
- 1 cup shredded sharp cheddar cheese
- 3 green onions, thinly sliced
- Saltine crackers or crusty bread
Instructions
- Melt the butter in a large heavy pot over medium heat. Add the onion and celery and cook gently, stirring now and then, for 8 to 10 minutes, until soft and sweet but not browned.
- Add the potatoes, broth, salt and pepper. Bring to a boil, then lower the heat, cover partly and simmer for 15 to 20 minutes, until the potatoes fall apart when pressed with a spoon.
- Pour in the milk, and the cream if using. Heat gently until steaming, without letting it boil hard.
- Push a potato masher straight down into the pot 8 to 10 times, around the pot, mashing about a third of the potatoes into the broth and leaving the rest in chunks.
- Simmer gently for 5 more minutes, stirring, until thick and creamy. If it gets too thick, add a splash of milk. Taste and add salt.
- Ladle into bowls and top each with cheddar, green onion and black pepper. Serve with crackers.
