Add first nine ingredients to a large bowl and stir with spoon (or use your hands) until all ingredients are thoroughly combined. Then, scoop out scant 1/4 cup measurements of meat and roll them into balls - about 8 (2 for each sub).
Place on a lightly greased, foil-lined baking sheet. Bake for 13-15 minutes or until nice and golden brown.
In the meantime, add marinara sauce to a small saucepan and warm through on medium-low heat. Keep on low once it's hot.
When the meatballs are done, remove from the oven and place in marinara sauce to coat before placing in bun. Alternatively, top your buns with meatballs and then cover with marinara sauce.
Top meatballs with mozzarella and Parmesan cheese, pop back in the still warm oven to melt a bit, and serve immediately. If your buns are large like the ones pictured, cut them in half before serving.
recipe and photos by Dana Shultz / concept by Brandi Koskie