Chilled potato leek soup is known as vichyssoise. According to one folk tale, King Louis XV of France’s paranoia is responsible for the soup being served cold. As a way of testing his favorite soup for traces of poison, it was tasted by several servants before he would eat it. By the time the soup was deemed safe to eat, it was no longer hot and King Louis decided he liked it better this way. Though this story is amusing, it is more likely that Chef Louis Diat created vichyssoise while working at New York’s Ritz Carlton between 1910 and 1920. The chef was often challenged to find a cool dish to serve on the Ritz’s rooftop garden during the hot summer months. As a young boy in France, Chef Diat ate his mother’s hot leek and potato soup and would cool it down by adding milk. This inspired him to create a chilled version he called “creme vichyssoise” after a spa located near his hometown. Though he originally planned to only serve the soup during the summer, it was so popular that he put it on the menu full time.
Of course, hot potato leek soup goes back further than Chef Diat; after all, he was eating his mother’s recipe as a child. Recipe variations appear in Escoffier’s Guide Culinaire (1903) and the Royal Cookery Book by Jules Gouffe (1869). Escoffier adds cream, while Gouffe thickens his with bread and butter. Even further back, a related dish called Cawl Kenin (or Cawl Cennin) bears similarities to modern potato leek soup. This Welsh stew with potatoes, leeks, meat and broth dates back to the 14th century. Considered by many to be the national dish of Wales, Cawl Kenin is often thickened with oats or flour and flavored with salted bacon.
The recipe that appears below is my take on potato leek soup, served piping hot with smoky undertones from a generous sprinkling of smoked paprika. It’s such a comforting meal on a chilly evening. Many potato leek soups are made with cream, but here I’ve used milk to cut on calories a bit. If you’re craving a really decadent soup feel free to substitute 1 cup of cream for 1 cup of the milk. Personally I find it plenty rich and satisfying with milk. If you’re feeling inspired by Chef Louis Diat you can add more milk to chill it, however I wholeheartedly recommend serving it hot.
Wondering how to clean and prep those funny-looking leeks? I’ve provided a full tutorial here.
- 2 1/2 lbs yukon gold potatoes, peeled and diced
- 4 cups vegetable stock
- 3 medium leeks, cleaned and sliced (learn how here)
- 1 1/2 cups whole milk
- 2 tbsp unsalted butter
- 1 1/2 tbsp cornstarch
- 3/4 tsp salt
- 1/2 tsp fresh thyme, chopped
- 1/2 tsp smoked paprika
- 1/4 tsp pepper
You will also need
- stockpot, large saucepan, small mixing bowl, whisk
- In a stockpot, combine diced potatoes and vegetable stock. Bring to a boil, then reduce to a simmer. Cook until the potatoes are very soft, about 25 - 30 minutes.
- Melt butter in a large saucepan. Add leeks and cook over medium heat, covered, until tender, about 15 minutes. Stir halfway through.
- Once the leeks are tender, add thyme, smoked paprika and pepper. Stir and cook for an additional 1-2 minutes.
- In a small mixing bowl, whisk together milk and cornstarch. Add to leek mixture and cook until thickened, stirring frequently, for another 3-5 minutes.
- With a whisk or potato masher, mash the potatoes to create a slightly chunky texure to the soup, like a chowder. If you prefer a smoother soup you can use an immersion blender to puree it.
- Add the leek and milk mixture to the mashed potatoes and stir to combine. Simmer for 5-10 minutes and season with additional salt and pepper if desired. Serve hot. Garnish each bowl with a sprinkle of smoked paprika for an extra bit of flavor.