Rinse shrimp shells under cold, running water and dry with kitchen paper.
Heat a wok over medium heat. Add the oil and shrimp shells, stir-fry for 10 minutes or until the shells become fragrant. Turn off the heat, drain and discard the shells.
Add minced spring onion and stir-fry for 10 seconds. Transfer the sauce to a bowl.
Add the light and dark soy sauce, salt, and mix well.
Add 2 tbsp cooked shell oil to warm noodle, and mix well.