1. In a large bowl, whisk or stir together the sweetened condensed milk and the peanut butter cups.
2. In the bowl of an electric mixer with a whisk attachment, whip the heavy cream on medium-high speed until stiff peaks form. Gently fold the whipped cream into the sweetened condensed milk mixture, until thoroughly combined. Transfer to an airtight container and store in the freezer. (Will take about 6 hours or so until mixture is completely frozen.)