In a small bowl, mix 1 cup panko with ⅔ cup milk. Let it soak for 2 minutes until softened.

In a large bowl, add the lean ground beef, plain pork sausage, soaked panko mixture, egg, egg yolk, minced garlic, grated ginger, soy sauce, sesame oil, brown sugar, black pepper, white pepper, and scallions. Mix gently until just combined. Stop as soon as it comes together.

Use an ice cream scoop to portion evenly. Roll each portion by hand into smooth 1 ½-inch meatballs.

Heat 1 to 2 tablespoons neutral oil in a large skillet over medium heat. Brown meatballs on all sides, 6 to 8 minutes total, working in batches. They do not need to be cooked through yet. Transfer to a plate.

Reduce heat to medium-low. In the same skillet, whisk together gochujang, soy sauce, honey, rice vinegar, garlic powder, sesame oil, and water until smooth. Bring to a gentle simmer.

Return the meatballs to the skillet. Spoon sauce over each one. Cover and simmer for 12 to 14 minutes, turning once at the halfway mark. Internal temp should reach 165°F.

Uncover, increase heat to medium, and simmer 2 to 3 minutes until the glaze thickens and clings to the meatballs.

Transfer to a platter. Garnish with sesame seeds and sliced scallions. Serve over rice or as an appetizer.