Rehydrate the cellophane noodles in hot water according to package instructions.

Drain the noodles and set aside.

Thinly slice the beef into bite-sized pieces.

In a bowl, combine the sliced beef with grated garlic, soy sauce, sugar, sake, and gochujang.

Marinate the beef for 15 minutes.

Julienne the carrot and green pepper into thin strips.

Thinly slice the shiitake mushrooms.

Heat 2 teaspoons of sesame oil in a large skillet or wok over medium-high heat.

Add the marinated beef to the skillet and stir-fry until it changes color and is mostly cooked through.

Add the julienned carrots, green peppers, and sliced shiitake mushrooms to the skillet.

Stir-fry the vegetables until they are tender-crisp.

Add the rehydrated cellophane noodles to the skillet.

Season the mixture with salt and pepper to taste.

Swirl in the remaining sesame oil to coat the noodles and vegetables.

Stir-fry for another minute or two, until everything is well combined and heated through.

Serve the Japchae on a dish.

Sprinkle with ground white sesame seeds.