Perfect Juicy Turkey Burgers - The Pollan Family

Ingredients

• 2 pounds ground turkey (preferably dark meat)
• 4 teaspoons extra virgin olive oil plus extra for coating hands
• 1 tablespoon finely grated red onion
• 1½ teaspoons Dijon mustard
• 1 tablespoon finely chopped Italian (flat-leaf) parsley
• 1 clove garlic, minced
• 1 teaspoon ketchup
• Kosher salt
• Freshly ground black pepper
• 1 tablespoon freshly grated Parmesan cheese
• 2 tablespoons cold unsalted butter, cut into 6 pieces
• 6 slices Swiss, cheddar, or jalapeño Jack cheese (optional)
• 6 hamburger buns (preferably whole-grain)