1Preheat oven to 350 degrees F (175 degrees C). Lightly grease baking sheets.
2Cream 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.
3Drop 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.
4To 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.
Footnotes
Tip
Aluminum foil can be used to keep food moist, cook it evenly, and make clean-up easier.