1. In a medium saucepan, whisk together the maple syrup, soy sauce, apple juice, corn starch, ginger and cayenne pepper.
2. Place over medium heat and cook until just bubbly.
3. Salt and pepper to taste.
4. Add meatballs and toss to coat.
5. Cover, reduce heat to medium-low and continue cooking until meatballs are heated through (about 30 minutes).
6. Garnish with chopped scallion.