Cut the whelk into bite-sized pieces.
Julienne the cucumber, carrot, and onion.
Boil the somyeon noodles, rinse in cold water, and drain well.
Make the sauce by mixing gochujang (Korean red chili paste), vinegar, sugar, and soy sauce.
Combine the noodles with the vegetables, whelk, and the sauce. Mix well.
Serve in a bowl and sprinkle with sesame oil and toasted sesame seeds.