Clean the squid thoroughly and cut it into bite-sized pieces.
Slice the tofu into 2cm thick pieces.
Heat cooking oil in a pan and grill the tofu on both sides until golden.
Push the tofu to one side of the pan and add the squid to stir-fry.
Add onion, green onion, chili peppers, and garlic, and stir-fry together.
Season with gochujang (Korean chili paste), soy sauce, sugar, and pepper, then stir-fry everything over high heat.
Transfer to a plate and finish by sprinkling with sesame seeds.