Season the sliced beef with salt, pepper, and sake. Massage the beef, then add cornstarch and mix well.

Tear the lettuce into bite-sized pieces. Slice the king oyster mushroom thinly after halving it lengthwise.

Mix the oyster sauce, sugar, sake, and chicken broth powder in a bowl to create the sauce.

Heat salad oil in a pan over high heat. Stir-fry the lettuce briefly and remove it from the pan.

In the same pan, heat sesame oil over medium heat. Add garlic paste and stir until fragrant, then add the beef.

Once the beef changes color, add the mushrooms and stir-fry until softened.