Add all marinara ingredients to a large soup pot. Place over medium heat and bring to a gentle simmer. Reduce heat to low and let the sauce cook slowly.
While the sauce begins simmering, add the ground beef, breadcrumbs, Parmesan, minced garlic, garlic powder, egg, salt, and pepper to a large mixing bowl. Gently mix until just combined, being careful not to overwork the meat.
Form the mixture into walnut-sized meatballs, aiming for about 24–26 total.
Carefully drop the meatballs into the simmering marinara. Cook on low for 1 1/2 hours, gently stirring occasionally. If the sauce becomes too thick, add a splash of water to loosen it.
About 30 minutes before the meatballs are finished, begin the polenta.
In a large pot, add the chicken broth, water, and polenta. Bring to a simmer over medium-high heat, stirring frequently. Cook for 15–20 minutes until thickened.
Reduce heat to low. Stir in the butter, heavy cream, and Parmesan cheese until fully incorporated. Continue cooking for another 15–20 minutes until creamy and tender.
Serve the meatballs and marinara spooned generously over the polenta. Finish with extra Parmesan and fresh basil.