"If you like Asian-inspired noodle dishes, you will love Korean japchae. You would never know that these satisfying noodles are made from sweet potatoes and are gluten free! Serve with kimchi as a garnish."
Combine 1/4 cup soy sauce, mirin, 1 tablespoon sesame oil, garlic, and 1 teaspoon pepper in a bowl. Add steak; stir to coat. Marinate for at least 30 minutes.
Combine 1/4 cup soy sauce, honey, 1 tablespoon sesame oil, and 1 pinch pepper in a large bowl; stir sauce well.
Fill a large pot with water and bring to a rolling boil; stir in noodles and return to a boil. Cook uncovered, stirring occasionally, about 5 minutes. Drain. Add noodles to sauce; toss to coat.
Whisk egg in a bowl. Heat a skillet over medium-low heat; pour in egg. Cook until firm, about 1 minute per side. Slice into strips.
Bring a large pot of lightly salted water to a boil. Add spinach and cook, uncovered, until just bright green, about 1 minute. Drain in a colander and immediately immerse in ice water for several minutes to stop the cooking process. Drain.
Heat olive oil in a large skillet over medium-high heat. Add carrot and onion; saute until tender, about 5 minutes. Stir in steak and marinade; cook until tender, 5 to 8 minutes. Stir in spinach. Add noodles and egg; cook and stir until well combined and heated through, about 2 minutes.