Put octpus in a large bowl. Add flour and scrub vigorously for about 2 minutes until it foams. This process not only tenderizes the octopus but also cleans any dirt or mud stuck in the suckers.

Rinse in cold running water until it’s not slippery anymore. Drain.

Bring a pot of water to a boil. Blanch the octopus for 10 to 12 seconds, drain, and then transfer to a cutting board.

Cut the heads and arms into bite size pieces. Set aside.

Make seasoning sauce:

Combine all the seasoning ingredients (hot pepper flakes, soy sauce, sugar, potato starch, rice syrup and ground black pepper) in a small bowl.Mix well with a spoon.

Heat up a large pan over high heat. Add vegetable oil.
Stir in garlic, ginger, green chili pepper, onion, and green onion for about 3 minutes until the garlic turns a little brown and the onion translucent.

Add nakji and seasoning sauce. Stir for 2 to 3 minutes.

Remove from the heat and stir in sesame oil. Transfer it to a serving plate.