Chef John's Chicken Spaghetti

Details

Ingredients

• 1 (4.5 pound) whole chicken, giblets removed
• 1 (24 ounce) jar marinara sauce
• 6 cups water
• 2 anchovy fillets
• ½ teaspoon red pepper flakes, or to taste
• 2 teaspoons salt, plus more to taste
• 1 (16 ounce) package spaghetti
• ¼ cup thinly sliced basil leaves
• ½ cup grated Pecorino Romano cheese
• 1 tablespoon cold butter
• 1 tablespoon grated Pecorino Romano cheese