Banana Cake with Panocha Frosting

INGREDIENTS

• 1 2/3 cup pastry flour
• 1 3/4 - 2 cup powdered sugar
• 2 eggs, separated
• 1/4 cup milk
• 1 cup brown sugar
• 1/4 teaspoon baking powder
• 2 bananas, crushed
• 1/2 cup butter
• 1/2 cup chopped nuts (optional)
• 1/2 teaspoon salt
• 1 teaspoon baking soda
• 1/2 cup sour milk
• 1 1/2 cup sugar