Small boxes of Jello in this order:
2 c sour cream (1½ lb)
Combine one box of Jello with 1¼ cups boiling water. Divide this mixture in half. To the first half, add 1/3 cup sour cream and stir until smooth. Use wire whisk to add sour cream. Don't make it too foamy. Pour into a 9x13 pan and pop any bubbles before putting it into the fridge. Refrigerate 40 minutes. To the second half of the mixture, add 3 Tbsp of cold water. Carefully spoon onto first layer. Chill 40 minutes. Repeat 10 times. Top with cool whip.
Note: Be careful as you pour on each layer. (See how my yellow Jello-sour cream layer sunk a little into the plain yellow layer?) Increasing the time to 40 minutes (from the original 30 minute recommendation made my layers solid enough to handle the next layer easily.
Make sure your fridge is level or make it level under the dish using paper. Use a level for best results.