Adapted from MFK Fisher’s How to Cook a Wolf
- 2 onions, sliced thin
- 4 medium potatoes, peeled and thinly sliced (1.33 lbs | 600 g, roughly)
- 2 tablespoons flour
- 4 tablespoons butter
- salt and pepper to taste
- 3 cups milk, 2% or whole
- chopped herbs such as parsley or chives, optional
- Sauté the onions in 2 tablespoons of the butter over medium to medium-low heat for 15 minutes, or until tender and just beginning to turn color. Add the potatoes and water to cover, about 2½ cups. Simmer until tender, about 20 minutes.
- In a separate pot, melt the butter over medium heat. Add the flour and stir with a wooden spoon until a light brown paste forms, a minute or so. Roux should be gently bubbling. Slowly add the milk, whisking constantly. Bring milk mixture to a gentle simmer, stir, then keep warm.
- When potatoes are tender, add milk mixture to the pot. Use an immersion blender to purée until smooth or transfer mixture to food processor or blender (be careful with blender — I don’t like using my blender for hot soups because I’ve had the top go shooting off and soup spraying everywhere). Season with salt (at least a teaspoon) and lots of fresh cracked pepper. Bring soup to a gentle simmer, stirring to ensure it isn’t sticking to bottom of pot. Taste and adjust as needed with more salt or pepper. Add herbs if using. Thin with more water or milk if necessary.
- When reheating the soup, thin with water as needed and adjust seasoning to taste.