In a large skillet, brown the ground beef over medium-high heat. Drain off any excess fat.

In a small bowl, whisk together the soy sauce, brown sugar, sesame oil, rice vinegar, minced garlic, ground ginger, and black pepper.

Pour the sauce over the browned beef in the skillet. Stir well to combine.

Reduce the heat to low and simmer for about 5-10 minutes, or until the sauce has thickened slightly. Stir occasionally.

Preheat your oven to 350°F (175°C).

Slice the croissants in half horizontally.

Place the bottom halves of the croissants on a baking sheet.

Spoon the Korean BBQ beef mixture generously onto the bottom halves of the croissants.

Sprinkle the shredded mozzarella cheese evenly over the beef.

Place the top halves of the croissants on top of the filling.

Bake in the preheated oven for 8-10 minutes, or until the cheese is melted and bubbly and the croissants are lightly golden brown.

Remove from the oven and garnish with sliced green onions and sesame seeds.

Let them cool slightly before serving.