Yeast helps give these waffles their signature crispy texture.
Put 1 cup plus 2 tablespoons flour, 5 teaspoons yeast, and 1/3 cup water into the bowl of an electric mixer fitted with the paddle attachment. Mix to combine. Transfer to a large bowl. Cover loosely with plastic wrap, and let rest 12 hours.
Stir together milk and remaining 5 teaspoons yeast in a small bowl. Let stand until foamy, about 5 minutes.
Put remaining 2 1/2 cups flour, the butter, eggs, vanilla, and flour-yeast mixture into the clean bowl of electric mixer fitted with the dough hook. Add milk-yeast mixture; mix on medium speed 1 minute. Add granulated sugar and salt. Raise speed to high; mix until batter pulls away from sides, about 10 minutes.
Add amber sugar, and mix 30 seconds. Cover loosely with plastic wrap, and let stand in a warm place until doubled in bulk, about 30 minutes.
Heat a waffle iron until hot. Drop 2 tablespoons batter onto each mold. Cook until golden, about 3 minutes. Let cool completely on a wire rack. Dust with confectioners' sugar.
Waffles can be stored in an airtight container up to 1 week.