Butter or oil a 9 x 13 pan lightly.
To make filling, bring the two cups of milk to a boil. Dissolve the 1 cup sugar into the milk.
In a small bowl, mix 1/2 cup cold water with 2 envelopes of unflavored gelatin.
Add gelatin mixture to the milk while still warm. Pour sour cream into a bowl and add in the gelatin/milk mixture.
Add in 2 tsp vanilla extract.
Keep mixture covered on the counter.
Make first package of jello. Pour into the cake pan. Place pan into the fridge.
Allow to set up, but make sure it is still a bit tacky to touch as this helps the next layer stick to it.
Add 1 1/2 cups filling for the next layer. Put back into fridge until set.
Repeat by making next package of jello, then 1 1/2 cups filling, and so on.
Keep in fridge until ready to eat! Enjoy!!