world famous pumpkin bars (for all the ghouls)

Ingredients

• 2 cups flour
• 2 teaspoons baking powder
• 1 teaspoon baking soda
• 1/4 teaspoon salt
• 2 teaspoons cinnamon
• 1/4 teaspoon nutmeg
• 2 cups sugar
• 1 cup chopped walnuts
• 1 cup salad oil
• 4 large eggs
• 1 can pumpkin (16 oz)
• FROSTING
• 1 package 3 oz. cream cheese
• 1 teaspoon vanilla
• 1 teaspoon milk
• 6 tablespoons butter
• 2 cups powdered sugar