Ingredients 2 cups packed brown sugar 3/4 cup butter 2 eggs 1/2 teaspoon salt 1 teaspoon ground cinnamon 1 teaspoon baking powder 3 tablespoons boiling water 1 teaspoon baking soda 2 1/2 cups all-purpose flour 2 cups quick cooking oats 1 egg white 2 tablespoons milk 1 teaspoon vanilla extract 2 cups confectioners\' sugar 3/4 cup shortening Directions Preheat oven to 350 degrees F (175 degrees C). Lightly grease baking sheets. Cream butter or margarine with the brown sugar until light and fluffy. Beat in the eggs and mix well. Stir in the salt, cinnamon, baking powder, boiling water, baking soda and flour. Mix to combine. Stir in the oats. Drop cookies onto the prepared baking sheets. Bake at 350 degrees F (175 degrees C) for 10 to 12 minutes. Let cookies cool then make sandwiches from two cookies filled with Whoopie Pie Filling. To Make Filling: Beat egg white. Mix in the milk, 1 teaspoon vanilla and 1 cup confectioners\' sugar. Beat in the shortening and remaining 1 cup confectioners\' sugar. Beat until light.