To begin, cook the glass noodles according to the package instructions, typically by boiling them in water for 7–8 minutes until tender. Drain and rinse under cold water to stop the cooking process. Toss with 1 tbsp sesame oil to prevent sticking and set aside.

Prepare the vegetables and protein. Julienne the carrot and bell pepper, slice the onion and mushrooms thinly, and blanch the spinach in boiling water for 1 minute. Squeeze the spinach gently to remove excess water and season it with a pinch of salt and ½ tsp sesame oil. If using meat, marinate it with 1 tbsp soy sauce, ½ tsp sugar, and ½ tsp minced garlic for 10 minutes.

Heat a large skillet or wok over medium heat and add 1 tbsp vegetable oil. Stir fry the carrots for 1–2 minutes until slightly softened. Remove and set aside. Repeat this process with the onion, bell pepper, and mushrooms, cooking each vegetable separately for even texture and flavour.

In the same skillet, cook the marinated meat over medium-high heat until browned and fully cooked, about 3–4 minutes. Remove from the skillet and set aside.

Combine the cooked noodles, stir fried vegetables, spinach, and cooked meat in a large mixing bowl. In a separate small bowl, mix the soy sauce, sugar, sesame oil, garlic, sesame seeds, and black pepper to create the seasoning sauce. Adjust sweetness or saltiness to taste.

Pour the seasoning sauce over the noodle and vegetable mixture. Using your hands or tongs, toss everything together gently to ensure the noodles and vegetables are evenly coated with the sauce.

Return the mixture to the skillet and stir-fry briefly over medium heat for 2–3 minutes to allow the flavours to meld. Taste and adjust the seasoning with a little more soy sauce or sugar if necessary.

Transfer the Japchae to a serving plate and garnish with thinly sliced egg omelette, additional sesame seeds, and chopped scallions. Serve warm or at room temperature, accompanied by kimchi or pickled radishes for a traditional touch. Enjoy the vibrant flavours and textures of this beloved Korean dish.