Use 1 yellow cake mix with pudding in mix. Bake according to package directions with batter divided between 2 round pans. Allow both to cool on wire racks. Slice each layer in half horizontally (so there are now 4 layers).
Filling:
5 Tbsp flour
1 cup water
1 stick margarine
1 cup sugar
2 tsp vanilla
1/2 cup Crisco
In a medium pan, mix flour and water. Boil until thick, then remove from heat and cool. When cooled, add in remaining ingredients and beat until thick and fluffy. Put filling mixture between layers and then sprinkle top of cake with powdered sugar.