My warming and hearty lime and lemongrass sweet potato soup features a rich coconut broth flavored with fragrant makrut lime leaves and refreshing lemongrass.
From fall until winter, we make soups a few times a week. I had plenty of sweet potatoes leftover from the root vegetable tarte tatin from a couple days ago and made a big pot of lime and lemongrass sweet potato soup. The recipe was adapted from my roasted kabocha squash soup. It features a rich coconut broth flavored with makrut lime leaves and lemongrass from our garden. We also grew sweet potatoes for the first time but they're not ready for harvest yet.
- Lemongrass: much of the lemongrass’s flavor is concentrated in its lower, cane-like stalks. Look for firm, pale-green stalks with fat, bulbous bottoms. Trim off the spiky tops and the bases and crush the stalks with the side of a knife to release their aromatic oils.
- Makrut lime: they are one of the most aromatic herbs and a wonderful addition to many soups, curries, and desserts. We grow our own but you can find them in the fresh herb section at many Asian grocery stores. Look for fresh makrut lime leaves that are dark green, shiny, and without any browning or yellowing.
- Aromatics: for the aromatics, I kept it simple with ginger, garlic, and shallot.
- Coconut cream: look for coconut cream, not coconut milk. The flavor you get from coconut cream is much richer. My favorite brands are Savoy and Aroy-d.
Tips for Making the Soup
- Roasting the sweet potatoes at a high temperature concentrates the sweet potato’s flavors and softens its flesh yielding a smooth texture.
- Cut the sweet potatoes into ½ inch rounds and toss them with olive oil, salt, and pepper. Lay them in a single layer in a prepared baking pan and roast at 400 degrees F for 30 minutes.
- While the potatoes are roasting, prepare the coconut cream. Add coconut cream, ginger, lime leaves, and lemongrass to a small saucepan and bring to a boil over medium-high heat. Turn the heat down to medium-low and let it simmer for 20 minutes to let the flavor infuse.
- Use high speed blender to get that ultra creamy texture. You can also use an immersion blender but the result is a coarser feel.
In less than an hour, you’ll have a pot of delicious and hearty soup ready for your family. This lime and lemongrass sweet potato soup is creamy and fragrant with a subtle sweetness from the roasted sweet potatoes. Round out the meal with a slice of warm bread or salad. Warming and hearty, my soup is perfect for those cold days.
Lime and Lemongrass Sweet Potato Soup
- 2 pounds sweet potatoes, peeled and cut into ½ inch rounds
- 4 tablespoons olive oil
- ½ teaspoon salt
- ⅛ teaspoon freshly ground pepper
- 1 400 ml (14 oz) coconut cream
- 4 cups vegetable broth
- 1 lemongrass stalk, cut into 2 inch batons, smashed
- 3 makrut lime leaves, crushed
- 1 inch knob ginger, smashed
- 2 garlic cloves, roughly chopped
- 1 shallot, roughly chopped
- salt and pepper to taste
- ¼ cup cilantro for serving
- ¼ cup coconut yogurt for serving (creme fraiche or coconut cream)
- Preheat oven to 400 degrees F.
- Toss sweet potato with salt, pepper, and 3 tablespoons olive oil on a rimmed baking sheet. Arrange vegetables in a single layer. Roast until golden around the edges and tender, about 30 minutes. Remove from the oven and set aside.
- While the sweet potatoes are roasting, prepare the coconut cream. In a small sauce pan, combine the coconut cream, ginger, makrut lime leaves, and lemongrass over medium heat and bring the mixture to a boil. Reduce the heat to a simmer and let it cook for 20 minutes.
- Heat 1 tablespoon of olive oil in a large saucepan over medium-high heat. Add shallot and garlic and cook for 2 minutes or until fragrant.
- Add roasted sweet potato and vegetable stock to pan and bring to the boil. Reduce heat to medium and simmer for 10 minutes until sweet potato softens.
- Transfer sweet potato mixture to high speed blender and puree until smooth.
- Add sweet potato puree back into pan. Add coconut cream mixture and bring to a simmer for another 5 minutes. Season with salt and freshly ground pepper to taste. Thin soup with 1 tablespoon of water at a time for desirable consistency.
- When ready to serve, divide soup among serving bowls, swirl through a dollop of yogurt, top with cilantro, and freshly ground pepper if desired.