Japanese Sweet Potato Soup with Rosemary and Ghee

I've long been partial to the dry sweet potatoes like Kotobuki and Hannah partly because I've felt that they aren't as sweet as the moist ones, like Garnet and Jewel. Cooked into a soup, however, their sugars really do come forward, though not with the same thrust that the others do. I used Hannahs here, which have buff skin covering dry white flesh that discolors when cut. This isn't a problem if you're putting them directly in the soup pot. But if you're cutting them ahead of time, put the pieces in a bowl of water. The skins can be bitter, which is why I suggest peeling them. Ginger practically begs to be included in this soup, but I decided to go in a more western direction, omitting that rhizome in favor of grounding thyme and rosemary. The odd thing is that when the soup is done, garnished and sipped, I can swear I taste ginger.
By | December 01, 2015

Ingredients

SERVINGS: 4 Cup(s)
  • 2 teaspoons ghee, or 1 tablespoon each dark ghee and sesame oil
  • 1 onion, sliced
  • ⅛ teaspoon asafetida (optional)
  • 1 heaping teaspoon chopped rosemary
  • 1 big sprig of thyme, leaves stripped to make a rounded ½ teaspoon
  • 1 pound (2 or 3) Hannah or Kotobuki sweet potatoes
  • 1 teaspoon sea salt and freshly ground pepper
  • 4 cups water

Preparation

Melt the ghee in a soup pot and, when it's hot, add the onion, asafetida, rosemary and thyme. Give a stir and while they're cooking over medium heat, peel the sweet potatoes with a vegetable peeler, slice them into rounds and add them directly to the pot as you work. Continue to cook, stirring occasionally, until you see some coloring on the sweet potatoes. They will caramelize as they cook, which not only lends flavor but tempers their sweetness, so give them a good 15 or 20 minutes instead of the usual 5 or 7. Add the salt and water; bring to a boil, then simmer, covered, for 15 minutes. Let cool slightly, then puree, leaving a little texture if you wish or making it super smooth. Taste and add more salt if need be, but it should be fine.

FINISHING THE SOUP

You have options here. For sure, season each bowl with plenty of cracked pepper. Because this is a smooth-textured soup you might want to finish it with some tiny croutons, browned in ghee with minced rosemary until crisp, then added at the last minute.

Stirring a spoonful of sour cream or creme fraiche into each bowl of soup tempers the sweetness. I do that, then drizzle a few drops of tamari over each serving.

Chopped parsley always offers a clean and bracing counterpoint to sweetness.

A few drops of good balsamic vinegar would also be good. Smoked sea salt, as well.

Make a combo garnish: pepper, croutons, sour cream and soy sauce or smoked salt.

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Ingredients

SERVINGS: 4 Cup(s)
  • 2 teaspoons ghee, or 1 tablespoon each dark ghee and sesame oil
  • 1 onion, sliced
  • ⅛ teaspoon asafetida (optional)
  • 1 heaping teaspoon chopped rosemary
  • 1 big sprig of thyme, leaves stripped to make a rounded ½ teaspoon
  • 1 pound (2 or 3) Hannah or Kotobuki sweet potatoes
  • 1 teaspoon sea salt and freshly ground pepper
  • 4 cups water
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