Step 1

In a large bowl, whisk together the condensed milk and the Cool Whip.

Step 2

Add the chocolate milk and vanilla and continue whisking until combined.

Step 3

Place the Frosty mixture into a freezer-safe container. Cover tightly with a lid or plastic wrap and place in the freezer.

Step 4

Freeze for 3 hours, stirring once every hour, until the Frosty has reached the desired consistency.

Step 5

Spoon into glasses and serve.