This seemingly humble soup really steals the show - and comes in at just 256 calories per bowl.
Using peels for flavor
This recipe is more than just the normal bowl of pureed sweet potatoes, onions, broth, and herbs. The recipe is crafted to really highlight the sweet potato flavor.
It turns out, adding some of the peels to the soup intensifies the flavor. The peel also contains about 30% of a sweet potato's fiber, making it an even healthier soup.
How to not water down the soup's flavor
Another key part of this recipe is to reduce diluting the soup with extra liquid. Normally a soup with starchy potatoes requires a lot of liquid to thin it out.
But thanks again to the research team at Cooks Illustrated, they found that when you let the potatoes sit in hot water (off the burner) for 20 minutes before boiling them, the starch molecules form differently. This step creates a creamy, thinned soup.
Whereas the typical method of adding potatoes to boiling water and holding them at a simmer, creates a loose mash with the same amount of water (thus requiring even more water to thin it into a soup and diluting the flavor).
Speaking of not diluting the flavor, this recipe uses water instead of broth. If you're scoffing at this and already plan to substitute broth (like I always find myself doing), resist! Really, this is the one time where water is the winner because it doesn't muddy that pure sweet potato flavor we are after.
- 3 Tbsp unsalted butter
- 1 shallot
- 4 sprigs fresh thyme
- 4 ½ cups water
- 2 lbs sweet potatoes reserve peels
- 1 Tbsp brown sugar
- ½ tsp cider vinegar
- ½ tsp pepper
- 1 ½ tsp salt
- 1 Tbsp chives optional
- Sweet potatoes: Peel the potatoes and reserve ¼ of the skins (those will go in the soup). Cut sweet potatoes in half, then slice into ¼ inch half-rounds.
- Shallot: thinly slice
COOK THE AROMATICS
- Melt butter in your favorite soup pan. Add shallots and thyme. Cook for about 5 minutes, until soft. Then add the water and bring to a simmer.
COOK POTATOES & FINISH SOUP
- Remove the pan from the heat. Add sweet potatoes and reserved peels to the pan. Let stand, uncovered, for 20 minutes. This cooks the sweet potatoes without making them overly starchy.
- Put the pot back on the stove and add the brown sugar, vinegar, 1.5 tsp salt and ½ tsp pepper. Bring to a simmer, then reduce the heat to low, cover, and cook until potatoes are very soft. This will take about 10 minutes.
- Remove the thyme sprigs. Then puree the soup with an immersion blender, or user a regular blender for an ultra-smooth soup.
- Add more liquid if needed. Season with salt and pepper if needed. Top with chives (or any other topping), if you are so inclined.
More about Nutrition
While I shared my version of a healthy soup, everyone has a different definition. I want you to be able to customize this recipe to meet your health goals, so I have provided a breakdown of calories and sugar per serving, for each ingredient below.
Carbs: sweet potatoes and white (russet) potatoes have the same amount of total carbs. In sweet potatoes, the carbs come from sugar and starch. In regular potatoes, the carbs are primarily from starch as they have almost no sugar.
Sugar: while sugar is a bit high in this recipe, the added sugar is very low, only 3g from the brown sugar. The majority comes from the sweet potatoes. The amount of added sugar should be limited to 25-30g a day (according to the American Heart Association).
Low glycemic index: boiled sweet potatoes actually have a lower glycemic index than regular white potatoes. But it is also worth noting that if a sweet potato is baked instead of boiled, the glycemic index goes from roughly 45 to 110.
Vitamin A: Thanks to the sweet potatoes, this recipe has over 100% of your daily value of vitamin A. It is fat-soluble, so don't skip the butter in this recipe!
I am a big fan of Cooks Illustrated which really digs into the science of recipes to find the perfect balance of flavor and effort. Their recipes never let me down. You can also check out Milk Street, which is a new magazine (and website) started by the previous founder of Cooks Illustrated.