Preheat oven to 350°F. Mix graham cracker crumbs, melted butter, sugar, and salt until sandy. Press into muffin liners.
Bake crusts 8–10 minutes until golden. Cool completely.
Whisk egg yolks until creamy. Slowly add condensed milk, lime juice, lime zest, and vanilla.
Divide filling evenly into cooled crusts. Smooth tops.
Refrigerate 4 hours (or overnight) until firm.
Beat cream to soft peaks, then add powdered sugar.
Pipe or spoon whipped cream onto pies, garnish with lime zest, serve.