Preheat oven to 350 degrees. Line 12 cupcake cups with paper liners.
Mix together crumbs, sugar and butter. Divide evenly among cupcake liners and press to make 12 little crusts.
Prepare Filling: Mix the condensed milk and sour cream until smooth. Stir in the lime juice, vanilla and zest. Divide the batter evenly among the mini pie crusts and bake for 7 minutes – they probably won’t look done, as they do not brown. Let cool at room temperature, then chill thoroughly.
Top with whipped cream and a stemmed cherry or slice of lime.