Set out 32 2-oz disposable shot glasses.
In a medium-sized bowl, use a knife to stir together cookie crumbs and melted butter until combined.
Press 1 ½ - 2 tsp of crumb mixture into the bottom of each shot glass.
Prepare your filling.
In a Kitchen-Aid/stand mixer (or using a hand-mixer), beat cream cheese until smooth.
Add sweetened condensed milk and beat until combined.
Gradually stir in key lime juice, stirring on low-speed until combined. Be sure to pause occasionally to scrape the sides and bottom of the bowl.
In a separate (clean) bowl, beat heavy cream until stiff peaks form.
Fold/slowly stir whipped cream into key lime mixture until completely combined.
Pour the mixture into a large ziploc bag and snip off one of the bottom corners. Pipe the filling on top of the gingersnap crusts in the shot glasses, filling each shot glass ¾ of the way full.
Before serving, prepare your whipped cream topping.
In a medium-large sized bowl, combine heavy cream, powdered sugar, and vanilla extract.
Whisk on high-speed (preferably with an electric mixer, otherwise your arm will get very tired very fast) until stiff peaks form.
Dollop or pipe whipped cream on top of each shooter.
Garnish with lemon zest and/or gingersnap crumbs, if desired.