01 - Preheat oven to 350°F. Line an 8-inch square baking pan with parchment paper, allowing an overhang on opposite sides for easy removal.
02 - Combine graham cracker crumbs, sugar, melted butter, and salt in a medium bowl. Mix until evenly moistened. Press mixture firmly and evenly into the bottom of the prepared pan.
03 - Bake crust for 8 to 10 minutes until lightly golden. Remove from oven and set aside to cool slightly while preparing filling.
04 - Whisk egg yolks and sweetened condensed milk in a large bowl until smooth and well combined. Add lime juice and lime zest; continue whisking until mixture thickens slightly, about 1 minute.
05 - Pour lime filling evenly over the warm crust. Return to oven and bake for 15 to 17 minutes until center is set but still slightly jiggly when gently shaken.
06 - Cool bars completely to room temperature, about 1 hour. Refrigerate for at least 2 hours or preferably overnight until fully chilled and set.
07 - Using parchment overhang, lift bars from pan. Cut into 16 equal squares. Top with whipped cream and additional lime zest or thin lime slices if desired.