Add all the meatball ingredients to a large bowl and mix well, use your hands. Shape into 1 1/2 inch balls (or as large as you wish) sticking a mozzarella cube in each meatball. You should get around 18 meatballs.
Place the meatballs in a casserole dish, then pour the cup of chicken broth over them. This will keep them from going dry and keep them moist. Bake the meatballs for 20 minutes.
In the meantime, prepare the pesto. Add all the pesto ingredients (minus the olive oil) to a blender, and pulse for about 10 seconds, with the motor running pour in the olive oil in a slow stream until emulsified. You will not be using all this pesto, see notes for how to store leftovers.
Cut the ciabatta buns in half crosswise then toast them only on the bread part, not the crust side, on a grill or under the broiler until golden.
To assemble the subs, spread some of the pesto on each bottom part of the bun, then spoon about 3 tablespoons of marinara sauce, sprinkle with some mozzarella cheese. Add 3 meatballs, 3 more tablespoons of marinara sauce, then more mozzarella cheese. Spread some more pesto over each top part of the ciabatta bun, before placing on top of the subs. You can place these in the oven for about 3 to 5 minutes at 400 F degrees until the sauce warms up and cheese melts.
You can store the leftover pesto in an airtight container or jar in the refrigerator for up to a week.
To store any leftover meatball subs, place them in an airtight container in the refrigerator for up to 3 or 4 days. Before serving, place them on a baking sheet and bake them for about 5 minutes at 400 F degrees or until heated through.
Please keep in mind that nutritional information is a rough estimate and can vary greatly based on products used.