Soak the tteokguk rice cakes in cold water for 10 minutes.
Chop the onion and green onion into small pieces.
Heat olive oil in a pan and sauté the onion and green onion.
Add the tteokguk rice cakes to the pan and stir-fry, then pour in a little water.
Add gochujang, gochugaru, soy sauce, and erythritol, and bring to a boil.
Simmer until the rice cakes become soft.