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Sweet Potato Noodles with Kale and Walnut Sage Sauce

The Calm Eats editor· Updated 16 Sep 2026· 5 min read
Sweet Potato Noodles with Kale and Walnut Sage Sauce
Recipe

Sweet Potato Noodles with Kale and Walnut Sage Sauce

Prep20 min
Cook15 min
Total35 min
Yield2 to 3 servings

Ingredients

  • 2 medium sweet potatoes, about 1.5 lbs (680 g) total, spiralized into noodles
  • 2 tbsp (30 ml) olive oil, divided
  • 1 bunch curly kale, about 6 oz (170 g), stemmed and torn into 2-inch pieces
  • 3/4 cup (85 g) walnut halves, toasted
  • 1/4 cup (10 g) fresh sage leaves, plus 8 to 10 whole leaves for frying
  • 2 cloves garlic, peeled
  • 1/3 cup (35 g) grated Parmesan, plus more to serve
  • 1/2 cup (120 ml) reserved starchy cooking water, plus more as needed
  • 1 tbsp (15 ml) lemon juice
  • 1/2 tsp fine salt, plus more to taste
  • 1/4 tsp black pepper

Method

  1. Bring a pot of water to a boil and salt it until it tastes like seawater, about 1 tbsp salt per 4 quarts (3.8 L). This water will also become the sauce base.
  2. Toast the walnuts in a dry skillet over medium heat, 4 to 5 minutes, shaking the pan often, until fragrant and one shade darker. Set aside to cool.
  3. In the same skillet, heat 1 tbsp (15 ml) olive oil over medium-high heat. Add the whole sage leaves and fry for 20 to 30 seconds per side until they stop bubbling and turn crisp. Remove to a paper towel; the oil is now sage-infused.
  4. Drop the kale into the boiling water and blanch for 90 seconds, until just wilted. Lift out with tongs or a spider and set aside, keeping the water at a boil.
  5. In a blender or food processor, combine the toasted walnuts, the 1/4 cup (10 g) fresh sage leaves, garlic, Parmesan, 1/2 cup (120 ml) of the hot cooking water, lemon juice, salt and pepper. Blend on high for 60 to 90 seconds until mostly smooth; it will still have some visible walnut texture.
  6. Heat the remaining 1 tbsp (15 ml) olive oil in a large skillet over medium-high heat until it shimmers. Add the sweet potato noodles in a single layer, working in two batches if the pan is crowded. Sear without stirring for 90 seconds, then toss and cook 2 to 3 minutes more, until the edges are browned and the noodles bend without snapping.
  7. Add the blanched kale to the skillet and toss for 30 seconds to warm through.
  8. Pour the walnut sage sauce over the noodles and kale. Toss to coat, adding cooking water 1 tbsp at a time if the sauce seizes or looks dry.
  9. Divide among bowls, top with the crisp fried sage leaves and extra Parmesan, and serve immediately.

Spiralized sweet potato behaves nothing like wheat pasta: it holds more water, it has no gluten structure to fall back on, and past a certain point of heat it turns from noodle to mash in under a minute. The whole method here exists to keep that window open long enough to build a sauce around it. Sear hard, don’t steam, and have your sauce blended before the noodles hit the pan.

Why the noodles go in the pan raw, not boiled

Boiling spiralized sweet potato is the fastest way to end up with orange mush. Raw sweet potato noodles are roughly 77% water by weight, and boiling adds more water while doing nothing to develop flavor. Searing in 1 tbsp (15 ml) of hot olive oil over medium-high heat drives off surface moisture instead of adding to it, which is why the noodles need to sit undisturbed in your pan for the first 90 seconds: moving them too soon traps steam under the strands and they go soft from the inside out. Left alone, the same strands hit 90°C to 100°C at the surface fast enough to brown and firm up before the center overcooks.

Building the walnut sage sauce without a stove

The sauce is a raw blend, not a cooked one, thickened only by the walnuts themselves and by starch carried over in the reserved cooking water. Toast the 3/4 cup (85 g) walnut halves in a dry pan for 4 to 5 minutes first; skipping this step leaves your sauce tasting flat and slightly bitter, since raw walnut skins carry tannins that toasting mellows. Blend the walnuts with 1/4 cup (10 g) fresh sage, 2 garlic cloves, 1/3 cup (35 g) Parmesan, 1 tbsp (15 ml) lemon juice and 1/2 cup (120 ml) hot starchy water for 60 to 90 seconds. It should coat the back of a spoon but still show flecks of walnut; if you see a fully smooth purée, it’s been over-blended and will taste more like paste than sauce.

Mushy noodles and a sauce that seizes: the two ways this dish fails

Mushy, watery noodles – the pan was overcrowded. Sweet potato noodles release water as they cook, and if too many go in at once that water can’t evaporate fast enough; it pools at the bottom of the pan and steams the strands instead of searing them. Work in two batches in a 12-inch (30 cm) skillet rather than one large batch, and resist the urge to stir for the first 90 seconds of each batch.

Sauce that seizes into a paste on contact with the noodles – the sauce was too thick going in, or the pan was too hot when it was added. Walnut sauces thicken quickly as they cool and the starch in the reserved water sets up fast. Add your sauce off direct high heat and loosen it 1 tbsp of hot cooking water at a time; going straight from blender to a screaming-hot pan cooks the Parmesan into clumps before the sauce can coat the noodles evenly.

Swapping the walnuts, the sage, and the one substitution that doesn’t work

Pecans or toasted almonds can replace the 3/4 cup (85 g) walnuts at the same weight; both are milder, so add an extra pinch of salt to compensate. Nutritional yeast, 3 to 4 tbsp, can stand in for the Parmesan for a dairy-free version, though your sauce will taste flatter and less rounded without the cheese’s salt and fat. Curly kale can be swapped for lacinato (dinosaur) kale at the same 6 oz (170 g) weight; lacinato is more tender and needs closer to 60 seconds in the boiling water rather than 90.

The one swap that doesn’t work: pre-packaged, thin (spaghetti-cut) spiralized sweet potato noodles sold refrigerated in most grocery stores. They’re cut thinner than a home spiralizer produces and have often sat in their packaging leaching moisture for days; they turn to mush in under a minute of searing regardless of pan heat. If you’re using store-bought noodles, pat them dry with a towel first and reduce the sear time to 60 seconds per side, checking constantly.

Questions cooks ask about sweet potato noodles

Can you make sweet potato noodles ahead of time?

Spiralize the raw noodles up to 24 hours ahead and store them submerged in cold water in your refrigerator, which prevents the cut edges from oxidizing and browning. Drain and pat them completely dry with a towel before searing; residual water on the surface is the main cause of steaming instead of browning.

Do sweet potato noodles need to be peeled first?

Peeling is optional. The skin holds its shape through searing and adds a slightly firmer bite and more fiber, but leaves flecks of skin throughout the dish that some diners find gritty. Scrub well under running water if leaving the skin on.

Why is my walnut sage sauce bitter?

Bitterness almost always traces back to under-toasted walnuts or scorched sage. Toast your walnuts only until one shade darker and fragrant, 4 to 5 minutes; beyond that the natural oils start to turn acrid. Fried sage should bubble for 20 to 30 seconds per side and no longer, since sage left in hot oil past that point turns bitter and dark rather than crisp and green.

Can this dish be made vegan?

Yes: replace the Parmesan with 3 to 4 tbsp nutritional yeast, both in the sauce and as the garnish. The texture of the sauce stays the same since the thickening comes mostly from the walnuts and starchy water, not the cheese, though the finished dish will taste less savory to you overall.

Storing the noodles and the sauce separately

Store leftover noodles and sauce in separate airtight containers in your refrigerator for up to 2 days; combined, the noodles continue absorbing moisture from the sauce and turn soft by day two. Reheat noodles in a dry skillet over medium heat for 2 to 3 minutes to re-crisp the edges before tossing with the sauce, which can be loosened with 1 to 2 tbsp of warm water directly from the fridge. This dish does not freeze well: thawed sweet potato noodles release enough water on defrosting to turn the whole dish watery and separated, so plan your portions before you cook.

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