Set ice cream out to thaw. I use 1/2 of a 1.5 qt of any kind of vanilla ice cream.
Place stick of butter in a 9x13 pan and melt in the oven on low temperature. While butter is melting, crush crackers with a rolling pin. Mix melted butter and crackers together and pat down evenly in the pan.
In a seperate bowl mix together pistachio and vanilla pudding with milk. Add a drop of green food coloring if desired. Fold in ice cream. Pour mixture over crumb crust and refrigerate for one hour to set.
After one hour spread Cool Whip on pudding/ice cream layer. If desired, sprinkle chopped nuts or cherries or shaved chocolate for decoration. Chill for couple hours before serving.