Khoai Lang Ken (Vietnamese Fried Sweet Potato Balls)
Vietnamese street snack: steamed sweet potato mashed with glutinous rice flour and coconut milk, wrapped around sweetened mung bean paste or mozzarella, shaped into cocoons and double fried for a crisp shell over a soft molten center.
Servings 6 servings
Ingredients
For the Dough
- 1 lb sweet potatoes peeled and cut into chunks
- ¾ cup glutinous rice flour plus more as needed
- ¼ cup rice flour
- 3 tablespoon granulated sugar
- ¼ teaspoon fine salt
- 3 tablespoon full fat coconut milk warm
- 1 tablespoon unsalted butter melted
For the Filling and Frying
- ½ cup sweetened mung bean paste or 3 oz low moisture mozzarella cut into 18 small cubes
- 4 cups neutral oil for deep frying
Instructions
Make the Dough
- Steam the sweet potato chunks 15 to 20 minutes, until a fork goes through with no resistance. Steaming keeps water out of the dough.
- Mash the hot potato with the melted butter until completely smooth.
- Add the sugar, salt, glutinous rice flour and rice flour, then the warm coconut milk. Work it with your hands into a soft, smooth, barely tacky dough. Add glutinous rice flour a tablespoon at a time if it sticks, or coconut milk a teaspoon at a time if it cracks.
Fill and Shape
- Divide the dough into 18 pieces. Flatten one into a disc in your palm, place a teaspoon of mung bean paste or a cube of mozzarella in the center, and draw the edges up over the filling.
- Pinch the seam shut and roll between your palms until the seam disappears completely. Any pinhole will blow out in the oil.
- Roll each ball on the counter with light pressure at the ends until it lengthens into a tapered oval about 2 inches long, fatter through the middle, like a silkworm cocoon. Set them on a tray, not touching.
Double Fry
- Heat the oil to 300F. Fry in batches of six for 6 to 7 minutes, turning gently, until pale gold and firm. Lift onto a rack and rest 10 minutes.
- Raise the oil to 360F and return the cocoons for 1 to 2 minutes, until the shells are deep gold and blistered.
- Drain on the rack for 1 minute and serve while the centers are still molten.
Notes
- Not banh tom: banh tom is a savory shrimp fritter made with raw julienned sweet potato. This dish is sweet, made from cooked mashed sweet potato bound with glutinous rice flour.
- Ken means silkworm cocoon: shape them as tapered ovals, not spheres.
- Seal completely: the most common failure is a leaking seam that bursts in the oil.
- The double fry: the first fry at 300F cooks the dough through, the 10 minute rest lets surface steam escape, and the short second fry at 360F crisps the shell.
- Filling: sweetened mung bean paste is traditional, low moisture mozzarella is the modern street version. Red bean paste also works.
- Make ahead: shape and refrigerate up to 24 hours, or freeze raw up to 2 months and fry from frozen at 290F for 9 minutes.