In a small bowl, break the bread up into small breadcrumbs with your hands. Add the buttermilk and heavy cream and mash into a paste. Let sit while you prepare the rest of the meatballs.
In a mixing bowl, combine the remaining meatball ingredients with your hands. Fold in the bread mixture until just combined. Cover and chill in the fridge while you make the sauce.
Preheat the oven to 400°F.
To make the sauce, in a large, cold skillet, place the oil, garlic and chile flakes. Turn the heat to medium and cook until the garlic is golden. Add the onion, peppers, oregano, salt and pepper and cook for 7-10 minutes, or until the veggies are soft. Add both canned tomatoes, sugar, and wine and bring to a boil. Reduce the heat to a simmer and cook for 20 to 30 minutes, until flavorful and thick. Season to taste and stir in the chopped basil.
Form the meat mixture into 2-inch meatballs and arrange in a baking dish with sides. Roast for 8 minutes, turn the meatballs, and continue to cook until they register an internal temperature of 165°F. Pour the sauce into the baking dish and cook for another 25 minutes.
Meanwhile, in a large pot, bring the water, milk, butter and salt to a boil. Reduce heat to low and whisk in the polenta. Cook, stirring regularly, for 20 minutes. Fold the feta and parmesan into the polenta and cook for 10 more minutes, until melted. Season with salt and pepper.
To make the vinaigrette, combine all of the ingredients except the oil in a blender, food processor, or immersion blender. You may also do this by hand using a whisk. As the mixture is blending, slowly add the oil to emulsify. Season to taste.
In a large bowl, toss together the radicchio, arugula, olives and balsamic vinaigrette.
Divide the polenta between plates. Top with meatballs and sauce and serve with salad on the side.