Sweet Potato Waffles

INGREDIENTS

• 1/2 teaspoon salt
• 1 cup milk
• 1 1/2 cups peeled and cubed sweet potatoes
• Special equipment: steamer basket and waffle iron
• 6 egg whites, at room temperature
• 2 cups all purpose flour
• 1 tablespoon baking powder
• 1 tablespoon grated orange rind
• Vegetable spray, for waffle iron
• 1/4 cup firmly packed light brown sugar
• 1/4 cup butter, melted