Sweet Potato (Yam) and Ginger Soup

Since about February our church has been getting together every Tuesday evening for supper. There’s always bread, and most often a soup to accompany it. I try to make the accompaniment go with whatever items are on sale during the week, and try to find some informative article related to them.

This week, sweet potatoes are on sale, both the yellow and the orange kind. (I just learned that what Americans call “yam” is not a true yam, but another variety of sweet potato.) There’s always simply baking the yams in an oven. I prefer a slightly more complicated version that maximizes starch conversion into sugar. I’ve made gratins with it.

Well, what about a soup?

I suppose I could have gone to one of the recipe sites or one of my cookbooks to find recipe for one, but what’s the fun in that? I wanted to see how different methods of preparing the sweet potato, and how different combinations of ingredients affect the end result. So with that in mind, I brought together --

• Fresh sweet potatoes (yams)
• Canned sweet potatoes (to see if they would be acceptable substitutes for fresh)
• Carrots
• Ginger
• Vegetable oil
• Butter
• Salt
• Ground cumin
• Garam Masala

I cooked the sweet potatoes in the following ways --

• Baked (peeled, sliced, covered)
• Boiled #1 (bring to fast boil, simmer until done)
• Boiled #2 (simmer at low-ish heat until done)
• Opened a can

All the above were then pureed and liquified in a blender. I steamed some carrots and pureed them also. Each puree was seasoned with a bit of salt.

I started with just the sweet potato purees and had Elise and the girls taste test them. I then added the carrot puree to one and had them test. I then added grated, fried ginger (2 kinds, one in plain vegetable oil, the other in butter) and had them tested. I added the cumin, another test; then sprinkled the garam masala for another. I mixed in a bit of cream for the final test.

It was definitely a fun experience, both for me, the cook, and for the testers.

The result? I thought that because we prefer the more complex baked sweet potato, it would work too, in a soup. But I was a little surprised to discover that for soups, a more plain, true sweet potato flavor is preferable. So as far as preparation, Boiled #1 was the winner.

However, there is an exception. As more complex spices were added, the baked, then pureed preparation began to balance the flavors out better.

I recommend passing on the canned sweet potatoes. It has a “processed” flavor to it and doesn’t have the complexity or the freshness that the freshly prepared ones do. It might do in a pinch, but not recommended.

The addition of carrots was a mixed bag. It didn’t work when it was just the sweet potatoes and the carrots by themselves. Once ginger and cumin was added, the preference for it became equal to just the sweet potatoes.

As for the ginger preparation, the ginger-butter combination appeared to have a slight edge by giving the soup a mellower flavor.

So for tomorrow night, assuming the store has adequate stock of fresh sweet potatoes, we will be having sweet potato and ginger soup, prepared as follows:

1. Peel and large dice sweet potatoes. Place in large pot and add enough water to barely cover them. Bring to a boil over high heat, then lower heat, cover and simmer until done, about 20-25 minutes.
2. Carefully pour contents into a blender and puree until smooth. (If a large amount, you may need to divide and do this multiple times.) You may need to add more water if the puree is too thick. Clean out pot and fill with contents of blender.
3. In a small skillet, melt 1 tbsp. butter, then fry ginger for about a minute. Add butter-ginger to sweet potato puree.
4. Thin out soup, if needed, with more water (or chicken stock). Add salt to taste. Bring back to a simmer.