Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
In a large mixing bowl, combine the panko breadcrumbs and milk and let stand for 5 minutes until the liquid is absorbed.
Add ground beef, ground pork, egg, Parmesan, garlic, parsley, basil, salt, pepper, and red pepper flakes to the breadcrumb mixture; mix with your hands until just combined — do not overwork.
Using a cookie scoop, form 1.5-inch meatballs, place on the prepared baking sheet spaced 1 inch apart, drizzle with olive oil, and bake for 20–25 minutes until golden and the internal temperature reaches 160°F (71°C).
While the meatballs bake, bring the broth to a boil in a large heavy-bottomed pot over medium-high heat, then reduce to a gentle simmer and slowly whisk in the polenta in a steady stream.
Reduce heat to low and cook, stirring every 5–7 minutes and scraping the bottom, for 30–35 minutes until the polenta is thick, creamy, and no longer gritty; add warm broth or water if it gets too thick.
Remove from heat and stir in the milk, butter, and Parmesan until the butter is fully melted; season with salt and pepper to taste.
Heat 2 tablespoons of olive oil in a skillet over medium-high heat and sear the baked meatballs for 1–2 minutes per side until deeply golden.
Spoon creamy polenta into shallow bowls, top with 3–4 meatballs, and garnish with fresh basil, extra Parmesan, and red pepper flakes; serve immediately.