October 5, 2011

Biochemistry at Work: Green Soup with Yams and Sage

So biochemistry. Yeah. That's my final post-baccalaureate class before applying to grad school. It requires me to write two essays a week. About biochemistry. My brain hurts. I've never written such science-focused papers before, but it's great practice for nutrition writing, which will be a breeze compared to this. It is pretty interesting material though. I'm currently learning about enzymes. I now understand how refrigeration keeps food fresh longer. (Enzymes, which are proteins that catalyze reactions, are temporarily unfolded (denatured) because they are only active in a narrow temperature range. I love knowing how that.) (I'm perfectly okay with being a nerd.)

In unrelated news, I appear to be on a kale kick. Who knew kale was so versatile? Before the October issue of EatingWell magazine I had only ever used it in Portuguese Kale and Sausage Soup (which is delicious, and I will have to share that recipe with you soon).

This time I used lacinato kale (versus the frilly kale--not sure what that's called) to mix things up.

This soup is really, really good. I will be making it again, possibly for company, so come over if you want some, and while you're here, tell me where I can find a Japanese yam on the Upper East Side. Though you don't need a Japanese yam for this recipe--I used your standard sitting-there-in-the-store-a-block-away-from-me yam. And the soup turned out great. Great, I tell ya. It's not hearty enough to be a meal (poor Graybeard actually had to step foot in the kitchen to forage for more food later that night), but I think it would be great as a first course for a dinner party or alongside a sandwich.

This recipe makes a lot, so you might want to halve it. I ate this for days and loved it, and only stopped when it started to look more brown than green (after about 3 or 4 days), though I would've kept eating it if more enzymes had been denatured (i.e., if it had stayed green).

Green Soup With Yams and Sage
Slightly adapted from EatingWell magazine

  • 3 tablespoons extra-virgin olive oil, divided
  • 2 large onions, chopped
  • 1 teaspoon salt, divided
  • 2 tablespoons plus 4 cups water, divided
  • 4 cloves garlic, sliced
  • 1 teaspoon chopped fresh thyme leaves or 1/2 teaspoon dried
  • 1 large bunch Tuscan, lacinato or Russian kale (As I mentioned in the Kale Chips post, EatingWell says to choose organic kale when possible because nonorganic can have high pesticide residue.)
  • 2 medium or 1 very large Japanese yam or regular sweet potato (about 1 1/4 pounds)
  • 14 cups gently packed spinach (about 12 ounces), any tough stems trimmed
  • 8 fresh sage leaves or 1 teaspoon crumbled dried
  • 4 cups vegetable broth, store-bought or homemade (I used homemade, which I think makes a huge difference in recipes. If you have the chance to make your own, I highly recommend it. It's super easy and totally worth it, especially if you make roast chicken a lot.)
  • Pinch of cayenne pepper
  • Freshly ground pepper to taste
  • 1 tablespoon fresh lemon juice, or more to taste
  • 16 fried sage leaves for garnish (Optional. Skip to the end of the recipe to see how to make these.)

1. Heat 2 tablespoons oil in a large skillet over high heat.
2. Add onions and 1/4 teaspoon salt. Cook, stirring frequently, until the onions are beginning to brown (about 5 minutes).

3. Reduce the heat to low and stir in 2 tablespoons water, garlic, and thyme and cover. Cook, stirring frequently until the pan cools down, and then occasionally, always covering the pan again, until the onions are greatly reduced and have a deep caramel color (25 to 35 minutes).
4. Meanwhile, remove tough stems and ribs from kale and coarsely chop the greens. Peel yam (or sweet potato) and dice into 1-inch pieces. Coarsely chop spinach and set it aside.

5. Combine the remaining 4 cups water and 3/4 teaspoon salt in a soup pot or Dutch oven. Add the kale, yam (or sweet potato), and sage. Bring to a boil. Reduce heat to maintain a simmer, cover, and cook for 15 minutes.

6. Stir in the spinach, return to a simmer, cover, and cook, stirring once halfway through, for 10 minutes more.

7. When the onions are caramelized, stir a little of the simmering liquid into them, then add them to the soup. Add the broth and return to a simmer. Cover and cook for 5 more minutes.
8. Puree the soup in the pot with an immersion blender until perfectly smooth or in a regular blender in batches (return it to the pot).

9. Stir in cayenne, a few grinds of pepper, and 1 tablespoon lemon juice. If the soup is sweet to your taste, add more lemon juice. Garnish each bowl of soup with 2 fried sage leaves.

Fried Sage Leaves
To make these heat about 1/2 inch olive or canola oil in a small saucepan over medium-high heat until shimmering but not smoking.
Add sage leaves; fry just until crisp, 1 to 3 minutes.

Drain in the strainer then spread out on a paper towel until ready to use. 

Eat up, and let me know how it turns out!


  1. I usually don't make recipes that require more than six items, however, in this case I may have to make an exception. Looks and sounds delicious! And the photos are very enticing, too.

  2. Awesome soup! Just serve with a steak next time. :)

  3. I'm learning about enzymes too! I'm with you, my brain hurts, but I'm loving it! The soup looks and sounds amazing! I know you'll doing great writing the papers with kind of fuel!