This recipe has already been posted, but here is a modification to make it freezer-friendly.
2 pounds ground chicken
1/2 tsp salt
1/4 tsp pepper
2 tsp rosemary
1 tbsp minced garlic
1 tsp crushed red pepper flakes
1 1/3 cups (~10 oz) ricotta cheese
2/3 cup grated Parmesan cheese
1 cup bread crumbs
In a large mixing bowl, combine the chicken, salt, pepper, rosemary, garlic, crushed red pepper flakes, ricotta cheese, parmesan cheese, egg, and bread crumbs. (If the mixture seems too wet, add a bit more bread crumbs.) Form 16 meatballs, wrapping each in wax paper (or you can flash freeze them on a wax paper-lined baking sheet). Place in freezer bag.
**These are meant to be big, as the main component of a meal (rather than a normal meatball with spaghetti). :)
Thaw meatballs. Preheat oven to 400 degrees. Lightly grease two baking sheets with about 1 tbsp olive oil. Arrange 8 balls on each of two baking sheets and coat them with olive oil. Roast for about 20 minutes, turning over halfway through. Serve meatballs with sauce on top or underneath.
Original recipe: http://momtestedkidapproved.blogspot.com/2009/01/mozzarella-stuffed-roasted-chicken.html