Heat oven to 400 degrees F. Line a large rimmed baking sheet with foil and spray with cooking spray.

In a large bowl, combine ground beef, bread crumbs, 1 teaspoon ground ginger, pepper, salt, 3 green onions, 2 minced garlic cloves, egg, and 1 tablespoon gochujang until well mixed. Roll into 1-inch balls and place 1 inch apart on the prepared baking sheet.

Bake for 20-25 minutes until meatballs are cooked through.

Meanwhile, in a medium saucepan over high heat, bring ¼ teaspoon ground ginger, 4 minced garlic cloves, soy sauce, ½ cup water, brown sugar, 1 tablespoon gochujang, rice wine vinegar, vegetable oil, and red pepper flakes to a boil.

Whisk cornstarch and 1 tablespoon water together in a separate bowl until well combined; stir into boiling sauce until just combined.

Reduce heat to medium; simmer and stir constantly for 8-10 minutes until sauce is thickened. Remove from heat.

Add the meatballs to the sauce and gently stir to coat. Serve meatballs warm topped with remaining green onion, sesame seeds, and cooked rice if desired.