Banana Squares

Ingredients

• 2 eggs, separated
• 2/3 cup shortening
• 1-1/2 cups sugar
• 1 cup mashed ripe bananas (2 to 3 medium)
• 1-1/2 cups all-purpose flour
• 1 teaspoon baking soda
• 1/4 cup buttermilk
• 1/2 teaspoon vanilla extract
• 1/2 cup chopped walnuts, optional