In a small bowl, whisk together maple syrup and confectioners' sugar until smooth. In a small saucepan, heat 6 tablespoons butter over medium, swirling pan occasionally, until golden brown and most of the foam has subsided, 8 to 10 minutes. Immediately pour into maple mixture and whisk until mixture forms a ribbon when you lift the whisk. Cover with plastic wrap and set aside.

Heat a waffle iron according to manufacturer's instructions. Lightly coat with cooking spray. Pour 1 1/3 cups batter onto iron and close; cook until waffle is golden and crisp, about 8 minutes. Transfer to a wire rack set in a rimmed baking sheet. Repeat with remaining batter.