Meatballs Al Forno

Ingredients

• 3/4 cup diced day- old, crustless bread
• 1/4 cup whole milk
• 1 1/2 cups freshly grated parmigiano- reggiano (about 6 ounces), plus a wedge of parmigiano-reggiano for grating
• 1/2 large yellow spanish onion, minced (about 1 cup)
• 2/3 cup finely chopped fresh italian parsley leaves
• 2 extra- large eggs
• 4 large garlic cloves, minced
• 2 to 3 teaspoons pure ground red pepper flakes, plus more to taste
• 2 teaspoons kosher salt
• 1 teaspoon freshly ground black pepper
• 1 pound ground pork (preferably pork butt)
• 1 pound ground veal
• 6 1/2 ounces pancetta, finely chopped or minced in a miniature food processor
• all-purpose flour, for dredging (about 2 cups)
• 1/4 cup extra- virgin olive oil, plus more as needed
• 1 quart passata de pomodoro (recipe follows) or tomato sauce
• 1 quart chicken stock
• 3 dried bay leaves
• 3 dried arbol chiles
• buttered semolina toast, for serving (optional)
• passata di pomodoro
• 2 28-ounce cans whole peeled plum tomatoes, including their juices (such as san marzano)
• 1/4 cup extra virgin olive oil
• 1 tablespoon sugar, plus more as desired
• 1 scant tablespoon kosher salt
• 1 heaping teaspoon freshly ground black pepper