To prepare meatballs, combine first 9 ingredients in a large bowl; shape mixture into 16 (1 1/2-inch) meatballs.
Heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray. Add 8 meatballs to pan, and cook for 6 minutes, browning on all sides. Remove meatballs from pan, and arrange on the rack of a broiler pan coated with cooking spray. Repeat procedure with the remaining 8 meatballs.
Bake at 425° for 7 minutes or until done.
To prepare the sauce, combine soy sauce, basil leaves, green onions, juices, 1 1/2 teaspoons water, mirin, and red pepper in a small bowl. Serve sauce with meatballs. Garnish with basil leaves and additional chopped green onions, if desired.