3 ½ pounds bone-in chicken pieces (or use a 31/2 pound chicken cut into 8 pieces)
2 teaspoons kosher salt
1 teaspoon black pepper
1 tablespoon extra-virgin olive oil
5 ounces pancetta, diced
3 garlic cloves, thinly sliced
2 anchovy fillets
¼ teaspoon red pepper flakes
1 (28-ounce) can whole plum tomatoes
1 large basil sprig, plus more chopped basil for serving
8 ounces bocconcini, halved (or use mozzarella cut into 3/4-inch pieces)