In a large bowl whisk together the condensed milk and the Cool Whip.
Add the chocolate milk and vanilla and continue whisking until combined.
Place the frosty mixture into a freezer-safe container. Cover tightly with a lid or plastic wrap and place in the freezer.
Freeze for 3 hours stirring once every hour, until the frosty has reached the desired consistency.
Spoon into glasses and serve.
If you have an ice-cream maker you can use that instead of putting the frosty mixture into the freezer.
I used regular 1% chocolate milk but chocolate almond milk will also work in this recipe.
If you don’t have a freezer safe container large enough to hold all of the frosty mixture, divide it up into 2 or 3 smaller batches to put in the freezer. Make sure you don’t fill the container to the very top, the mixture will expand a bit as it freezes. If you freeze the frosty mixture in smaller batches the freeze time will be slightly shorter.
I have made this using glass and plastic freezer containers. The mixture in the plastic freezes slightly faster than the mixture in the glass container.