For the meatballs: In large bowl, mix together the meatball ingredients until combined evenly (I use my hands). Roll into 40 balls (about 1 1/2-2 inches).
Space evenly on prepared baking sheet. Bake in a 425 degree oven for 20-25 minutes.
For the casserole: Pour half of the spaghetti sauce in the bottom of a 2qt baking dish. Top with meatballs. Pour remaining sauce over meatballs. Top with shredded parmesan and mozzarella.
Cover with foil and bake in a 375 degree oven for 30 minutes. Remove foil and bake an additional 5 minutes, until cheese is melted.
Serve as is, or with a pile of pasta. Also great on a sub sandwich!
Notes
Swap out the homemade meatballs for frozen meatballs instead.
You can bake the meatballs ahead of time and then freeze them for later. Freeze the cooled meatballs on the baking sheet, then transfer to an airtight container. When you’re ready to make the casserole, you can add the frozen meatballs right in; you’ll just need to add a few minutes of baking time.
These meatballs would be delicious with ground beef as well.
Cover the casserole dish with cling plastic wrap or transfer to an airtight container. Keep refrigerated until ready to reheat and eat!