Soak the noodles in warm water about 6-8 minutes. Don't soak in hot water or they will be mushy.
Make the sauce by combining all ingredients except the cornstarch and water, and whisking together. Set aside.
Add 1 tablespoon of cooking oil to a large skillet over medium heat. Add onions and cook for 5-6 minutes, until softened but not browned.
Add the garlic and cook for 30 seconds.
Add the carrot and cabbage and cook for 2-3 minutes, until softened but still having a crunchy bite to them.
Mix together with cornstarch and cold water. Add the sauce, the cornstarch mixture, and the noodles. Stir. Cook for 2 minutes, stirring until the sauce has thickened and everything is covered in the sauce.
Turn the heat off and add the sesame oil.
Serve and garnish with sliced green onions, sesame seeds and sriracha hot sauce.
Notes
Substitutions - Try Sambal Oelek or Sriracha hot sauce in place of the Gochujang paste if you can't find it.Storage - Stores in the fridge in a container with a lid for 3-4 days. Reheat in the microwave on reheat setting for a few minutes.