01 -
Set oven temperature to 400°F and line a baking sheet with parchment paper.
02 -
In a large bowl, combine egg, breadcrumbs, Parmesan, Italian seasoning, minced onion, garlic powder, salt, pepper, and water. Stir until incorporated. Add ground beef and turkey and mix gently with hands until just combined.
03 -
Divide mixture into 15 equal portions on a clean surface, then roll each into a ball using wet or lightly oiled hands. Arrange meatballs on the lined baking sheet.
04 -
Bake the meatballs for 15 to 20 minutes until cooked through.
05 -
When there are 5 minutes left in baking, pour pasta sauce into a saucepan, cover, and warm over medium-low heat. Reduce to low if sauce begins to bubble. Stir occasionally.
06 -
After baking, gently mix meatballs with pasta sauce, allocating approximately ¼ cup sauce per every 3 meatballs.
07 -
Move oven rack to the top position and switch oven to broil. Remove parchment paper; replace with aluminum foil on baking sheet. Split buns open and place on sheet. Fill each bun with 3 sauced meatballs and top with 2 tablespoons shredded Mozzarella. Broil for about 2 minutes until cheese melts and buns are lightly toasted—monitor closely to avoid burning.