While the sauce is simmering, prepare the meatballs.
Preheat the oven to 450˚F with a rack near the top of the oven. Line a sheet pan with parchment paper for easier cleanup.
Using a sharp chef’s knife, slice the partially frozen chicken lengthwise into thin slices. Set 3 or 4 of the slices on top of each other and, again, slice thinly into long strips. Turn the strips 45 degrees and cut again into a small dice (smaller than a pea). As you dice the chicken, add it to a medium-large bowl.
Add the egg, parmesan cheese, onion, garlic, panko, chopped herbs, sun-dried tomatoes, Italian season, salt and pepper to the bowl with the chicken.
Mix with your hands (or with a sturdy spatula) until everything is well blended.
With an ice cream scooper or a spoon, scoop the chicken mixture up into 12 portions.
Using wet hands, roll the chicken into balls and place on the prepared pan. Brush each meatball with olive oil.
Bake for 10 minutes.
Once the marinara has finished simmering, drop the meatballs in and bring to a simmer again. Simmer gently for another 10 minutes, uncovered, stirring occasionally.
Serve over pasta or polenta, as desired. Garnish with fresh basil.