Directions

1. In a large mixing bowl, combine cake and pudding mixes, oil, water and eggs; mix well. Pour into a greased and floured 13-in. x 9-in. x 2-in. baking pan. Bake at 350 degrees F for 30-35 minutes or until a toothpick inserted near the center comes out clean. Cool for 10 minutes; invert onto a wire rack to cool completely.
2. In a small saucepan, combine flour and milk until smooth. Bring to a boil; cook and stir for 2 minutes or until thickened. Cool. In a mixing bowl, cream the butter, shortening, sugar and vanilla; beat in milk mixture until sugar is dissolved, about 5 minutes.
3. Split cake into two horizontal layers. Spread filling over the bottom layer; cover with top layer. Cut into serving-size pieces. Freeze in an airtight container for up to 1 month. Remove from freezer 1 hour before serving.