– 4 (1.3 kg) boneless, skinless chicken breasts, 2½-3 pound – ▢Kosher salt – ▢Freshly ground black pepper – ▢¼ cup (60 ml) extra virgin olive oil – ▢1 onion, chopped – ▢4 garlic cloves, minced or grated – ▢3 oil-packed anchovies, chopped – ▢1 teaspoon dried oregano – ▢1 teaspoon ground fennel seed, optional if using Italian seasoning – ▢½ teaspoon crushed red pepper, or more/less to taste – ▢1 15-ounce (30 g) can crushed tomatoes – ▢1 cup jarred roasted red peppers, drained and chopped – ▢1½ cups shredded mozzarella cheese – ▢1 cup fresh basil leaves, torn or chopped