Chill a metal loaf pan and a mixing bowl for 10 minutes.
Whip the cold heavy cream to soft peaks. Keep it chilled.
Whisk condensed milk, pumpkin puree, vanilla, molasses, spices, salt, and bourbon until smooth.
Fold one-third of the whipped cream into the pumpkin mixture to lighten it.
Gently fold in the remaining whipped cream just until combined.
Stir in most of the crushed gingersnaps and crystallized ginger, reserving a handful for topping.
Spread into the chilled pan and scatter reserved crumbs on top. Cover tightly.
Freeze until firm, at least 6 hours or overnight. Let stand 5 minutes before scooping.