1.In a large bowl, soak the rice cakes in warm water for at least 5-10 minutes to acclimate them. Strain and set aside. In a small bowl, mix together dashi and cornstarch. Set aside.
2.Heat vegetable oil in a large non-stick pan on medium heat. Fry the chunjang in the oil for 1 minute constantly stirring it. Then add in onion, 2 green onions cut into 1-inch pieces and fish cakes. Mix until well combined.
3.Stir in cornstarch mixture until combined with other ingredients. Bring to a boil and reduce to a simmer for 5 minutes on medium heat or until sauce has thickened.
4.Mix in rice cakes then season with sugar and oyster sauce to taste. Simmer for 5-10 minutes until rice cakes are soft but chewy or fork tender. Remove off heat. Garnish with 1 green onion chopped and sesame seeds. Serve immediately.