01 - In a large mixing bowl, combine the ground beef, napa cabbage, onion, green onions, garlic, ginger, soy sauce, sesame oil, mirin, sugar, black pepper, and egg. Mix thoroughly until all ingredients are evenly distributed and the mixture holds together.
02 - Place a dumpling wrapper flat in your palm and spoon 1 rounded teaspoon of filling into the center. Moisten the wrapper edge with water, fold into a half-moon shape, and pinch firmly to seal, creating pleats along the edge if desired. Repeat with the remaining wrappers and filling.
03 - In a small saucepan, combine the gochujang, honey, soy sauce, rice vinegar, sesame oil, and minced garlic. Simmer over low heat for 2 to 3 minutes, stirring occasionally, until the glaze thickens slightly. Remove from heat and set aside.
04 - Heat 1 tablespoon of vegetable oil in a large nonstick skillet over medium-high heat. Arrange the mandu in a single layer without crowding. Cook for 2 to 3 minutes until the bottoms turn golden brown and crisp.
05 - Pour ¼ cup of water into the skillet and immediately cover with a lid. Steam for 3 to 4 minutes. Remove the lid and continue cooking until all the water evaporates and the bottoms regain their crispness, about 1 to 2 minutes more.
06 - Transfer the cooked mandu to a serving plate. Drizzle or brush generously with the warm gochujang glaze. Sprinkle with toasted sesame seeds and serve immediately while hot and crisp.