Add dashima and scallion whites to 2 1/2 cups of water in a deep pan or pot and bring to a boil.
While water is coming to a boil, add sesame oil, black pepper, gochugaru, and 2 tablespoons of gochujang to the rice cakes (they should be thawed if you're using frozen). Stir until the rice cakes are evenly coated and set aside.
When the water has come to a boil, add your rice cakes to the water, along with remaining gochujang. Cook for about 5 minutes, until the rice cakes are tender and the sauce has reduced to a thick stew consistency. Add your maple syrup and continue stirring until incorporated.
Garnish with scallion greens, sesame seeds, black pepper, and a drizzle of sesame oil.