
Add the sweetened condensed milk and Cool Whip together in a large bowl. Stir together until they are smooth and creamy.
Stir in the chocolate milk and vanilla, then continue stirring until all of the ingredients are combined and it resembles a thick chocolate milk.
Place the mixture into a freezer safe pitcher, preferably a plastic pitcher.
Freeze for 4-6 hours, stirring every hour. If you would like a thicker frosty, freeze for 6-8 hours.