Preheat oven to 350°F (175°C). Line an 8×8-inch pan with parchment paper.

Mix graham crumbs, sugar, and melted butter. Press firmly into the bottom of the pan. Bake for 10 minutes, then let cool slightly.

In a bowl, whisk together egg yolks, condensed milk, lime juice, and zest until smooth.

Pour filling over crust and bake 15–18 minutes, until just set.

Cool completely, then chill for at least 2 hours before slicing into bars.

Serve with a little whipped cream and a lime slice if you like!