Potato Soup - From Leftover Mashed Potatoes

Potato Soup is something I usually make with raw potatoes, as in my classic Potato-Leek Soup. But I had some leftover Mashed Potatoes the other day and thought I'd turn them into a soup. It's very thick and rich. You add as much liquid as you need at the end to get the consistency you prefer -- easier than getting it too thin and then having to thicken it. 

I recently got a high-performance blender (more about that another day) and have been having fun making hot soups in it. There's no heating element; it's powerful enough to make friction heat. At the same time the ingredients, even raw vegetables, are being transformed into a perfectly smooth and creamy blend, they are being heated.

Of course, you can just cook this on the stove and puree it right in the pan with an immersion blender. But you'll need to chop and cook the celery if you do. This is my new favorite way to use leftover mashed potatoes. Or baked or boiled potatoes, for that matter. Maybe not leftover french fries, though. But, then, who ever has leftover french fries!

What is your favorite soup? Have you ever heated soup in a high-performance blender? I'm looking forward to making more slow cooker soups this autumn and winter.

Potato Soup - From Leftover Mashed Potatoes

(Makes five 1-cup servings)

2 tablespoons unsalted butter
1/2 cup chopped onion
1 stalk celery*
2 cups leftover mashed potatoes
1 cup milk + more
1 cup lower sodium vegetable, chicken or beef broth + more
1/2 lightly packed cup shredded cheddar
1/2 teaspoon dried dill
1/4 teaspoon coarsely ground black pepper
1/8 teaspoon salt
Garnish options: dill, chives, scallions, sour cream, shredded cheese, crumbled bacon

* If using a high-performance blender, just break it in half and throw it in. Otherwise, chop it and cook it in butter with the onions. I suppose you could skip cooking the onion as well, but I can't eat raw onion so I cook it quite well.

1 In small skillet, melt butter. Cook chopped onion (and, perhaps, chopped celery) until softened, about 5 minutes.

2 Place in high-performance blender jar all the ingredients except the garnishes. Hit the preprogrammed Soup button. Taste and adjust seasoning. Hit the button again. Check the temperature and consistency. If it's thicker than you like, add more liquid. You'll need to hit the Soup button again to heat the added liquid.

3 Pour into bowls and garnish. I gave this bowl just a sprinkling of extra dill and coarsely ground black pepper and a bit of shredded cheese.