Bring a pot of water to a boil for the sweet potato noodles. While the water is boiling, make the peanut sauce. In a small bowl, combine the soy sauce, toasted sesame oil, sugar (or maple syrup), gochujang, rice wine vinegar and creamy peanut butter. Stir until smooth and glossy and set this aside to let the flavors meld. Then sauté the thinly sliced shiitake mushrooms in a splash of sesame oil until tender and golden.
Once the water is boiling, cook the sweet potato noodles according to the package directions. Keep a close eye on them as the noodles can turn sticky quickly if left too long. Drain and rinse with cold water to stop the cooking. Toss the noodles in the peanut sauce while they’re still slightly warm, coating every strand in the sauce.
To serve, scatter the sautéed mushrooms, bell pepper, cucumber and scallions over the noodles. Sprinkle on some sesame seeds for garnish and add a splash of fresh lime juice. Top the noodles with pan-fried sunny side up eggs, if you choose. Enjoy the noodles warm or chilled!