In a medium bowl, mix together condensed milk and vanilla extract.
In a stand mixer with a whisk attachment, beat heavy cream on high speed until stiff peaks form.
Fold whipped cream into condensed milk and vanilla mixture.
Once the whipped cream is fully incorporated with the condensed milk, stir in graham cracker crumbs, crushed graham crackers, chocolate chips and marshmallows.
In a small, microwavable bowl, melt peanut butter.
Line a 4 1/2 x 8/12 inch loaf pan with parchment.
Pour 1/3 of the ice cream mixture into loaf pan and drizzle about 1/3 of the melted peanut butter over the ice cream mixture.
Repeat two more times ending with the peanut butter on top.
Place loaf pan into the freezer overnight, or until firm.