Add cashews to a small mixing bowl and cover with very hot water to soak for 30 minutes. Then drain thoroughly and set aside. (Or soak cashews overnight or 6-8 hours in cool water).
If serving with kale chips or sautéed kale (or crispy chickpeas), prepare now and set aside until serving.
While cashews finish soaking, peel and spiralize potatoes using a veggie spiralizer on the thinnest blade. Or if you don't own a spiralizer, you can use a vegetable peeler or julienne peeler instead. Set aside.
Add soaked and drained cashews to a high-speed blender. Then add remaining ingredients: garlic, nutritional yeast, salt, arrowroot starch, and almond or rice milk.
Blend on high until creamy and smooth, scraping down sides as needed. Taste and adjust flavor as needed, adding more garlic for zing/kick, nutritional yeast for "cheesiness," salt for saltiness, or a pinch of red pepper flake (optional) for heat. The sauce should be creamy, smooth, and pourable. If too thick, thin with a bit more almond milk.
Transfer sauce to a large, rimmed pan or pot and heat over medium-low heat until it just starts to bubble. Whisk as it heats, as it will thicken. Once bubbling reduce heat to a very low simmer to keep warm. The sauce will thicken, so thin with more almond or rice milk as needed.
Add 1 inch water to a large pot and top with a steamer basket (if you don't have a steamer basket, see notes). Heat over medium-high heat and once bubbling, add potato noodles. Cover to let steam for 3-5 minutes or until al dente or a little softer (depending on taste). Be careful not to steam too long or the noodles can become soggy.
Serve as is or garnish with fresh parsley, crispy chickpeas, kale, vegan parmesan, or red pepper flake (optional).
*If you don't have a steamer basket, sauté sweet potato noodles in a bit of oil in a large rimmed skillet for 5-7 minutes, gently stirring / tossing until al dente or slightly more done (to taste). This method can be a little trickier to master as steaming is more controlled and even heat. But it still works!
*To save time you can also buy store-bought spiralized sweet potato noodles.
*Nutrition information is a rough estimate calculated without optional toppings or garnishes.
*I prefer the above linked spiralizer by Inspiralized. But this Spiralizer looks great, too!