Sweet Potato & Ginger Soup

Following along with our winter "what's-in-season" cooking theme is a wonderful root vegetable that keeps, like the hard spaghetti squash of last week, so well over the course of the winter.

Typical sweet potatoes available in our Canadian market

Sweet potatoes are a tad confusing because they come in so many shapes, sizes, colours and varieties... and because they are often confused with yams. They can be knobbly or smooth, long, skinny & pointy, or round and fat. Adding to the confusion is the fact that a sweet potato, despite being a tuber, isn't a potato at all! Sweet potatoes are New World vegetables and feature heavily in South American & Southern U.S. cooking. They are one of the oldest vegetables known and have been around since prehistoric times. Native to South America, they cook faster than white potatoes and can be baked, fried, boiled, nuked (microwaved), roasted and eaten raw. For the purposes of most recipes, the differences between them matter little.

Brigette, our SWEFM volunteer
coordinator, used to see Pete in
his Greengrocer's shop when she
lived in Halifax. It's a small world!

According to Pete Luckett, the most common variety of sweet potato in Canada is the copper skinned variety with bright orange flesh. The flavour will depend on the variety... as a general rule, lighter-fleshed sweet potatoes are more delicate, nutty rather than sweet, while darker ones have the distinctly spicy-sweet taste most of us would expect. He also advises that you never peel sweet potatoes, as their flesh darkens as soon as it is exposed to air. Simply wash them off, giving them a light scrub.

Sweet potatoes are wonderfully versatile... they can become delicious oven-baked fries, they can add thickness and be the sweet basis of delicious creamed soups and slow-cooked stews, they can be mashed and accompany a succulent chicken or turkey or ham roast, and they can even form the basis of pancakes or waffles! Yup, sweet potatoes are a great ingredient in your kitchen arsenal.

Still not convinced that they should be a part of your culinary repertoire? Then you have to consider the health benefits. A general rule when considering nutrition science in your home kitchen is that the more vibrantly coloured a fruit or vegetable is, the more packed it is with nutrients and antioxidants. That holds very true for the humble sweet potato. High in fibre (especially if you eat the skin), potassium, antioxidants, betacarotene and vitamins E, A & C, sweet potatoes help to arm you against heart disease & cancer and delay the effects of aging on the brain. And because sweet potatoes have so much fibre, they are a far better choice for diabetics than white potatoes because the fibre helps to keep blood glucose levels from spiking. So even though they have a far sweeter mouth taste, they have a lower glycemic index and are a far better choice.

Sweet Potatoes are more perishable than other types of potatoes because their skin is thin, delicate and susceptible to scraping and bruising. To avoid shortening their shelf life, The Sweet Potato Buyers Guide from A.V. Thomas Produce recommends that they be kept in a cool dry area with good air flow. Dampness and heat will cause them to spoil, so don't store them near a heat source and don't wash them until you are ready to use them. You might think this means you should refrigerate them, but DON'T! Refrigeration causes the inside of the potato to become hard and will affect its taste.

sweet potato & ginger soup

Frozen ginger grated with the Lee
Valley wood rasp.

This is a very creamy Thai soup, packed with flavour, that has been a favourite of mine for many years. Yup, it's a Thai recipe. 

We think of sweet potatoes as being a North American vegetable that goes hand in hand with a Thanksgiving feast, but did you know that sweet potatoes are even more popular in Asia with 90% of the sweet potato world export market being made up of sweet potatoes from there? 

They cook up very quickly (10 minutes), so they can be ready in a (culinary) heart beat! This recipe is so simple to make, but so creamy in a deliciously smooth, tangy, sweet way, that you just would't think it could possibly be good for you!

Just a little kitchen tip: when grating ginger root, I find it far easier to grate it from frozen. Buy ginger in bulk & put it in the freezer in a ziplock bag. It isn't messy or fibrous when you grate it in a frozen state (and yes, you can grate it with the skin on). I also use a wood rasp... yup, a wood working tool that I got from Lee Valley Tools years ago and it is incredibly sharp (another trick my father taught me). They now sell them with a metal catching trough on them that makes using the rasp in the kitchen a cinch. kitchen wood rasp. And fresh in for christmas stockings this year, they have a hand protecting container that slides along the rasp surface and collects ginger bits in a little glass bowl. Check it out... Zester Mate.

Coconut milk comes in small tins
that are the perfect size for this recipe.

Also, a little shopping tip: buying coconut milk can be a bit confusing as there are many varieties and price points from which to choose. I've found that there really isn't much of a difference between them, except when it comes to "lite" coconut milk (like cloudy water) and regular coconut milk (which has a heavy cream on top... give it a good shake before opening the tin). I usually make a trip to Lucky 97 downtown or T & T at West Edmonton Mall to stock up as it's far cheaper there than at your regular grocery store.  (While I'm there I also stock up on fresh kaffir lime leaves, lemon grass and ginger as they're all infinitely cheaper there and can easily be popped in the freezer & used later with no special prep & no ill effects whatsoever. Rice is far less expensive there too). At those Asian grocery stores, coconut milk can be found in small tins that are the perfect size for this recipe. 

Don't worry about buying "lite" coconut milk. It is used in a very small amount for this recipe, and despite being high in fat, saturated fat, regular coconut milk is high in the right kind of fat... medium chain triglycerides... that are essential for our health, so it is a very nutritious, heart happy, addition to this recipe.

Yield: 8-10 servings

3 simple ingredients... the soup
before blending with just sweet potatoes, stock & ginger.

ingredients

6 c. cubed, peeled sweet potatoes (peeling is optional)

3½ c. chicken or vegetable stock

1T. minced ginger root

½ c. unsweetened, light coconut milk

3T. fresh lime juice

½ t. salt

½ t. pepper

1/4 c. sliced almonds, toasted

1/4 c. chopped, fresh cilantro

instructions

1. In a saucepan, combine the potatoes, stock & ginger. Bring to a boil. Reduce heat, cover & simmer for about 10 minutes, or until the potatoes are tender.
2. Transfer to a food processor or blender, or use an immersion blender directly in the pot. Purée until smooth.
3. Return to the saucepan. Whisk in the coconut milk (be sure to scrape & include any of the yummy coconut cream that is stuck to the side of the tin), lime juice, salt & pepper. Cook over low heat until just heated through.
4. Ladle into bowls. 
5. Sprinkle with almonds & cilantro.

Vibrantly coloured, creamy & delicious...
this is the soup once it is puréed.

Info from The Greengrocer's Kitchen, by Pete Luckett, and from The 150 Healthiest Foods on Earth, by Jonny Bowden, Ph.D., C.N.S.
Recipe from Anne Lindsay's New Light Cooking, p. 66

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Contributed by Sheri Hendsbee