In a medium bowl combine 3/4 lb ground pork and 1/4 lb ground beef. Add 3 tablespoons soy sauce, 2 tablespoons brown sugar, 1 tablespoon mirin, 1 teaspoon sesame oil, the minced garlic, 1/2 teaspoon ground ginger (or 1/2 tsp minced fresh), 3 tablespoons sliced scallions, 1/4 cup grated onion, 1/4 teaspoon black pepper and 1/2 teaspoon gochujang if using.

Add 1 teaspoon potato starch or cornstarch to help bind. Mix thoroughly with a fork or your clean hands until the mixture is sticky and cohesive (about 1–2 minutes). Taste a small spoonful (optional — cook a tiny pinch in a skillet) and adjust seasoning: more soy for saltiness, more sugar for sweetness, or more gochujang for heat.

Cover and refrigerate the filling for at least 15 minutes (or up to 2 hours) to let flavors meld while you make the dough.

Dough & Assembly

Make the dough

In a mixing bowl whisk together 2 cups all-purpose flour, 1 teaspoon instant yeast, 1 teaspoon sugar and 1/2 teaspoon salt. In a separate cup combine 1/2 cup warm water and 1/4 cup warm milk (temperature ~100–110°F / 38–43°C). Whisk in 1 beaten egg and 2 tablespoons softened butter. Pour wet into dry and mix until a shaggy dough forms. Knead by hand on a lightly floured surface for 6–8 minutes or in a stand mixer with a dough hook for 4–5 minutes until smooth and slightly elastic.

Place dough in a lightly oiled bowl, cover with plastic wrap or a towel, and let rise in a warm place until doubled, about 45–60 minutes.

Shape rolls

Punch down the risen dough and turn it out onto a lightly floured surface. Divide dough into 6 equal pieces (for snack-sized) or 4 pieces for larger rolls. Roll each piece into a rough rectangle about 6 x 4 inches (15 x 10 cm). Place an even portion of the chilled bulgogi filling along the long edge of each rectangle, leaving a 1/2-inch border at the ends. Use your fingers to shape the filling into a sausage-like log about 3/4-inch in diameter.

Brush the uncovered edge of dough with a little beaten egg (from the egg wash) or water and roll the dough tightly around the filling, sealing the seam. Tuck the ends under to enclose the filling. Place seam-side down on a parchment-lined baking sheet, spacing 1–2 inches apart.

Final proof & egg wash

Cover the formed rolls loosely with plastic wrap or a towel and let them proof for 20–30 minutes until puffy. Meanwhile, preheat oven to 375°F (190°C). Beat the remaining egg with 1 teaspoon milk to make an egg wash. Brush the tops of the rolls with egg wash and sprinkle with 1 teaspoon sesame seeds.

Bake

Bake in the preheated oven for 16–20 minutes, or until the rolls are golden brown and an instant-read thermometer in the center of a roll reads 190–200°F (88–93°C). If tops brown too quickly, tent loosely with foil for the last 5 minutes.

Remove from oven and cool 5 minutes on the baking sheet, then transfer to a wire rack for another 5 minutes before serving. The filling will be hot — let rest briefly.

Optional Garnish & Serving

Serve warm with kimchi mayo or gochujang mayo for dipping and a small side of shredded lettuce or pickled daikon. These rolls are great as snack-size hand pies for parties or as part of a meal.