Maple Muffins - Once Upon a Chef

Ingredients

• 2¼ cups all purpose flour, spooned into measuring cup and leveled-off with a knife
• ¾ cup whole wheat flour, spooned into measuring cup an leveled-off with a knife
• 1 tablespoon baking powder
• ½ teaspoon salt
• 1½ cups pure maple syrup, preferably Grade B (Grade A works fine too)
• 12 tablespoons (1½ sticks) unsalted butter, melted
• ½ cup whole milk
• 1 large egg
• 1 large egg yolk
• 1 cup coarsely chopped walnuts, toasted if desired (optional)
• Softened unsalted butter, for greasing the pan