Preheat the oven to 400 degrees F. Line a baking sheet with parchment paper.
Combine the turkey
, Parmesan, pesto, salt, pepper and egg in a large mixing bowl with your hands, taking care to not overwork the meat. Form golf ball-size meatballs (about 24) and stuff each with 1 mozzarella cube
. Evenly space the meatballs on the baking sheet. Bake until just starting to brown, 15 minutes.
Add the Classic Tomato Basil Sauce and chicken broth to the slow cooker
. Transfer the meatballs to slow cooker, cover and cook on low 4 to 6 hours.
Allow the meatballs to cool slightly before serving, and adjust with salt and pepper, if necessary.