Defrost the frozen octopus in the refrigerator or microwave until partially thawed.

Clean the octopus by removing the internal organs, eyes, and beak. Rub with coarse salt to remove impurities.

Rinse the octopus under cold water and blanch in boiling water for 15 seconds. Immediately transfer to ice water.

Prepare vegetables: slice green onion, thinly slice onion, chop green chili, and blanch bean sprouts.

Mix red pepper powder, soy sauce, sugar, cooking wine, minced garlic, and sesame oil to create the sauce.

Heat a pan over high heat, add cooking oil, and stir-fry green onion to create aromatic green onion oil.

Add sliced onion to the pan and spread evenly. Cover and cook on high heat until caramelized.

Add the sauce, octopus, and green chili to the pan. Stir-fry until the octopus is cooked and the sauce is well combined.