Crust: Finely crush a sleeve of graham crackers and measure 1 cup of crumbs into a small bowl. Stir in the melted butter.
Divide crumb mixture between 12 small serving dishes and press down firmly.
Filling: Soften cream cheese and beat with a hand mixer in a mixing bowl till smooth and creamy. Gradually beat in the sweetened condensed milk, occasionally scraping the sides of the bowl.
Add the lime juice and zest and beat just till well blended. Pipe or spoon the filling over the crusts.
Topping: In a metal or glass bowl, beat cream with hand mixer till soft peaks form. Add powdered sugar and vanilla and beat till well blended. Spoon a dollop on top of each dish.
Serve immediately or chill for 2-3 hours. Garnish with lime slices or zest if desired.
Notes
You can assemble the crust and filling, cover and chill for 1-2 days. Add whipped cream before serving.