Cook evaporated milk and milk on medium heat until warm.  Remove 1/2 cup milk and set aside. Add sugar, butter and eggs and continue heating.  Mix flour and corn starch in milk that has been set aside.  Add a small amount of the heated milk mixture to the milk that has been set aside.  Mix well and add to pot.  Continue cooking stirring constantly until mixture comes to a slight boil (should take about 5 minutes).  Remove from heat and add vanilla.  Mixture should be as thick as heavy whipping cream.  Break crackers into mixture.  Stir and place in a serving dish.