Jellyfish Salad with Chinese Celery

Name: Jellyfish Salad with Chinese Celery
Ingredients: Three 5.2-ounce packages ready-to-eat or instant jellyfish, seasoning packets removed and reserved for another use (see Cook’s Note); Kosher salt; 2 tablespoons white sesame seeds; 3 tablespoons neutral oil, such as vegetable or grapeseed oil; 2 cloves garlic, thinly sliced; 2 scallions, thinly sliced, white and green parts separated; 1 teaspoon gochugaru (Korean red pepper flakes), optional; 3 tablespoons unseasoned rice vinegar; 1 tablespoon soy sauce; 1 1/2 teaspoons toasted sesame oil; 1 1/2 teaspoons sugar; 1/2 teaspoon ground white pepper; 3 ounces Chinese celery, thinly sliced on a diagonal (about 1 cup) plus 2 tablespoons roughly chopped leaves