Sweet Potato Soup Base
I got the idea from Lidia Bastianich to make soup bases that pack a lot of flavor on the weekend, then freeze them and thaw them as needed, adding various ingredients on the fly to take them in different directions. I like to concentrate the base, which saves freezer space, and then thin it out when I make a finished soup. Before you thin it out (and jazz it up) for the final soup, this base may remind you of a certain fluffy Thanksgiving side dish (minus the mini-marshmallows, thankfully), but there are some key differences. Besides the lack of cream or sugar, the most important one is the cooking method: Rather than boiling peeled cubes of sweet potato, I like to roast them, concentrating the complex flavor, which is highlighted by subtle hints of thyme and curry. This makes an especially vibrant backdrop to such treatments as Sweet Potato Soup with Chorizo, Chickpeas, and Kale (page 43). There are many other possibilities. You can sprinkle ground chipotle or pimenton (smoked Spanish paprika) for heat and/or smoke, or add toasted pecans, yogurt (or sour cream or crème fraîche), and other sausages or cured meats.
Recipe information
Yield
makes about 4 cups
Ingredients
Preparation
Step 1
Preheat the oven to 425°F.
Step 2
Use a fork or sharp knife to prick the sweet potatoes in several places. Place on a piece of aluminum foil and bake until the sweet potatoes are tender and can be easily squeezed, 60 to 75 minutes. (Alternatively, to speed up the process, microwave the pricked sweet potatoes on High for 1 minute, then carefully transfer to the oven on a piece of foil. Bake until the potatoes are tender, 30 to 45 minutes.)
Step 3
Pour the oil into a 3-quart saucepan over medium heat. When it starts to shimmer, add the carrots, celery, leek, thyme, and a pinch of salt. Stir to combine well, then decrease the heat to low, cover the pot, and allow the vegetables to sweat in their own juices until very soft, 10 to 15 minutes. (Take care not to allow the vegetables to burn.)
Step 4
Scrape into the saucepan the soft flesh from the roasted sweet potatoes, add the curry powder, and stir to combine, mashing the sweet potato flesh with a spoon. The mixture will be chunky. Stir in the stock and combine well. Bring the mixture to a boil, then decrease the heat so the mixture gently simmers, and cook, covered but with the lid slightly ajar, for about 15 minutes to let the flavors meld. Allow the mixture to cool slightly, then remove and discard the thyme.
Step 5
Use a handheld immersion blender to puree the soup base, which will be very thick. (Alternatively, you can puree it in a blender or food processor. If using a blender, be sure to remove the center cap on the lid and cover with a dish towel to let steam escape, and work in small batches to avoid splattering the soup.) Taste and add salt if needed.
Step 6
Let the soup base cool to room temperature. Divide it into 4 portions and use immediately, refrigerate for up to 2 weeks, or freeze in small containers or heavy-duty freezer-safe resealable plastic bags, pressing as much air out of the bag as possible before sealing. It will keep frozen for several months.
