Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9x13 inch pan.
In a large bowl, cream together the butter and sugar until light and fluffy. Beat in the eggs one at a time, then stir in the vanilla. Combine the flour, baking powder and salt; stir into the batter alternately with the milk.
Spread evenly into the prepared pan. Bake for 25 to 30 minutes in the preheated oven, or until a toothpick inserted into the center of the cake comes out clean.
In a medium bowl, mix together the cream cheese, confectioners' sugar and remaining 1 teaspoon vanilla until smooth. Spread onto the cooled cake.
Interesting Facts
The Twinkie was invented in 1930 by James Dewar, a baker for the Continental Baking Company.
The Twinkie has become a cultural icon, appearing in films, television shows, and books.
The original Twinkie was filled with banana cream, but due to a shortage of bananas during World War II the filling was changed to vanilla.