Prepare 10.6 oz of glass noodles, 10.6 oz of pork tenderloin (for japchae), 5.3 oz of carrot, 1/2 red bell pepper, 1/2 yellow bell pepper, 5.3 oz of shiitake mushrooms, 7 oz of onion, and 6.3 oz of spinach (half bunch). (You can choose or substitute vegetables according to your preference; for example, oyster mushrooms instead of shiitake, or chives instead of spinach are also good.)

Marinate 10.6 oz of pork tenderloin (for japchae) by mixing it with 1 tbsp of granulated sugar, 2 tbsp of soy sauce, 2 tbsp of cooking rice wine, 0.5 tbsp of minced garlic, 0.5 tbsp of sesame oil, and a dash of ground black pepper.

Lightly coat the largest frying pan with cooking oil (as needed) and preheat over high heat. Add the carrots and stir-fry for about 1 minute. Once the carrots are slightly cooked, add the onions, separating them, and continue to stir-fry over high heat. When the onions are slightly tender, add the bell peppers and stir-fry, then season lightly with 1 pinch of salt. Finally, add the washed spinach (without blanching) and stir-fry over high heat until it wilts. Transfer the stir-fried vegetables to a large bowl and spread them out to release moisture.

Turn on high heat in the same pan used for vegetables. Add the marinated pork and stir-fry thoroughly. You don't need to add extra oil. When the pork is about 80% cooked, add the shiitake mushrooms and stir-fry together. Continue to stir-fry until most of the moisture has evaporated and the pan feels almost dry. Then, transfer the stir-fried pork and mushrooms next to the vegetables and spread them out to release moisture.

Boil 2 L of water in a pot or wok. Add 10.6 oz of unsoaked dry glass noodles to the rapidly boiling water and cook. (About 8 minutes for high heat, 9 minutes for low heat is appropriate.)

Rinse the cooked glass noodles thoroughly twice in cold water to remove starch, then drain them well in a colander. Since japchae can become soggy if stir-fried in a small pan, it's best to use a large wok or frying pan (about 11-12 inches / 28-30 cm in diameter).

Place the drained glass noodles in a wok heated over high heat. Add 5 tbsp of soy sauce, 1 tbsp of granulated sugar, 1 tbsp of oyster sauce, 5 tbsp of corn syrup, and 3 tbsp of cooking oil, then mix well. Once the seasoning is thoroughly combined, maintain high heat and let the sauce reduce without stirring until it thickens. Once it has reduced somewhat, taste the noodles to check their doneness. (If you prefer them softer, adjust by stir-frying longer over medium heat.)

Continue to stir-fry the glass noodles until they feel like they are sticking to the pan and all moisture has completely evaporated. (Heat control is crucial here: start with high heat, then gradually reduce to medium-low heat.) Turn off the heat when the noodles feel cohesive like a 'tteok' (떡 - Korean rice cake).

Add the well-stir-fried glass noodles to the prepared stir-fried vegetables and pork (use sanitary gloves as it will be hot). Add 2 tbsp of sesame oil and a generous amount of ground black pepper, then mix everything thoroughly. Finally, sprinkle with sesame seeds for a delicious, soggy-proof japchae.