Banana Nut Layer Cake

Ingredients (20)

• 1/2 cup shortening
• 2 cups sugar
• 1 egg plus 1 egg white
• 1 cup buttermilk
• 1 cup mashed ripe bananas
• 1 teaspoon vanilla extract
• 2 cups all-purpose flour
• 1 teaspoon baking soda
• 1 teaspoon salt
• 1/2 cup chopped walnuts
• FILLING:
• 1/4 cup butter, cubed
• 1/2 cup packed brown sugar
• 1/4 cup all-purpose flour
• Pinch salt
• 3/4 cup milk
• 1 egg yolk
• 1 teaspoon vanilla extract
• 1/2 cup chopped walnuts
• Confectioners' sugar