Rinse the rice cakes under running water.
Mix the sauce ingredients (gochujang, soy sauce, erythritol, minced garlic) beforehand.
Pour water and sauce into a pan and bring to a boil.
When it boils, add rice cakes, fish cakes, and onion.
Simmer on medium-low heat until the rice cakes become soft.
Add scallions and boiled eggs, and cook for another 2-3 minutes.
Turn off the heat and transfer to a plate.