In a large bowl add condensed milk and vanilla extract and set aside.
Put cream in the bowl of stand mixer and beat with an electric whisk on high power until thick and quite stiff. The consistency of clotted cream.
Gently fold whipped cream into condensed milk mixture until smooth.
Add chopped mars bars and gently fold to evenly distribute.
Transfer to a freezer safe container with a lid or a loaf tin (covered with plastic wrap).
Freeze for at least 5 hours or until solid.