Tropical Icebox Cake

Gingersnap Crust: Place 2 1/2 cups loosely crumbled gingersnaps, 5T melted butter, and 3T sugar into a food processor and blend until mixture is the texture of coarse sand.
Ice-cream Layer: Soften 2 1/2 cups high-quality vanilla ice-cream or frozen yogurt and stir in 1 cup chopped pineapple and 2/3 cup loosely crushed macadamia nuts.
Whipped Cream Layer: Whip 1 1/2 cups of heavy cream sweetened with a few tablespoons of sugar and a splash or two of rum. Whip until billowy but not too stiff.
Toasted Coconut: I pan toasted the coconut over medium low heat, roughly a cup or so.
Assemble the cake: Pack a thin layer of ginger snap crust into the base of a 6-inch spring form pan. Slather on a generous layer of ice cream, let it freeze until hard.
Pack another layer of ginger snap crust on top of the ice cream (because I love the buttery sweet gingersnap crumbs), then fill pan to the rim with a thin layer of rum + sugar sweetened whipped cream.
Freeze until hardened, preferably overnight.
Release cake from the pan (don't cut around edges w/ a knife) and frost the entire cake with a layer of the sweetened whipped cream.
Top with toasted coconut. Put back in the freezer until outside layer of whipped cream is set.