He Added a Potato to Mushroom Soup but Rinsed It First: There’s a Reason

Mushroom soup often gets its creamy texture from milk, heavy cream, or flour, but one recipe uses a russet potato instead. The unusual part comes before cooking: the potato gets sliced and rinsed under cold water, removing excess surface starch that could affect the soup once it reaches the blender.

Cookbook author Wil Yeung uses this method in a dairy-free mushroom soup made with cremini mushrooms, onions, garlic, vegetable stock, and raw cashews. The potato adds body, while the cashews create a rich, smooth base without relying on cream.

Rinsing the potato may seem counterproductive when starch helps thicken soup. But the goal isn’t to remove all the starch. It’s to reduce the excess on the cut surfaces so the finished soup develops body without becoming gluey.

The potato goes into the pot after a cold-water rinse

Start with one medium russet potato, weighing about 10 ounces. Cut it into thin slices, then rinse the pieces under cold water and drain them.

Cutting exposes starch on the potato’s surface, which the water helps wash away. Starch remaining inside the slices still contributes to the soup’s texture during cooking.

Heat two tablespoons of olive oil in a stockpot over medium heat. Add one sliced white onion and two or three crushed garlic cloves, cooking for about seven minutes until softened and browned at the edges.

Add the rinsed potato slices, mushroom stems, and half the caps from a half-pound of cremini mushrooms.

Season with salt and black pepper, then cook for another four minutes before adding vegetable stock.

Simmer for approximately ten minutes, allowing the potato and mushrooms to soften before blending.

Cashews provide the cream without dairy

The recipe uses one-quarter cup of raw cashews to create a smooth base.

Blend the cashews with some of the recipe’s stock or water, salt, pepper, and a drizzle of olive oil until the mixture becomes smooth.

A high-speed blender can process the raw cashews without soaking. For a standard blender, soaking them overnight helps soften the nuts.

Add the cooked mushroom and potato mixture to the cashew cream in batches, taking care when blending hot soup.

The potato contributes thickness, while the cashews add richness and help create a smooth texture.

Return the blended soup to the pot after sautéing the remaining sliced mushroom caps in a tablespoon of olive oil for about three minutes.

Reserve a few mushrooms for garnish, then stir the rest into the soup.

The finished dish contains no milk or heavy cream, yet the combination of cooked potato and cashews produces a thick mushroom soup.

The important step happens before the potato enters the pot. Rinsing removes excess surface starch while leaving enough inside the slices to contribute body after cooking.