Trim the base of the king oyster mushrooms, rinse lightly under running water, pat dry with a kitchen towel, and cut into bite-sized pieces.

Slice the bell peppers thinly, chop the green onion, and mince the garlic.

Heat a pan over medium heat, add cooking oil, and sauté the green onion until fragrant to create scallion oil.

Add the sliced onions and stir-fry briefly over medium heat.

Add the bell peppers and mushrooms, season with a pinch of salt and black pepper, and stir-fry over high heat.

Mix soy sauce, oyster sauce, corn syrup, and minced garlic, then add to the pan and stir well.

Taste and adjust seasoning with additional salt if needed.

Turn off the heat, drizzle sesame oil over the dish, and mix well.