Prepare the oven and pie plate: Preheat the oven to 350°F (175°C). Place the 9-inch (23 cm) pie plate on a baking sheet to make it easier to transfer in and out of the oven.

Make the graham cracker crumbs: Crush the graham crackers into fine, even crumbs. If using a food processor, pulse until no large pieces remain. If using a resealable bag, crush them with a rolling pin.

Mix the crust: Combine the graham cracker crumbs, granulated sugar, and kosher salt. Pour in the melted butter and stir until all the crumbs are evenly moistened. The mixture should resemble damp sand and hold together when pressed.

Form and bake the crust: Press the crumb mixture firmly into the bottom and slightly up the sides of the pie plate. Use the flat bottom of a glass or measuring cup to compact it evenly. Bake at 350°F (175°C) for 8 to 10 minutes, until lightly golden and fragrant.

Cool the crust slightly: Remove the crust from the oven and let it cool for about 10 minutes while preparing the filling. Keep the oven at 350°F (175°C).

Prepare the lime filling: In a large bowl, whisk the egg yolks until smooth. Add the sweetened condensed milk, Key lime juice, lime zest, vanilla, and kosher salt. Whisk gently until the mixture is completely combined and smooth. Avoid whipping in excessive air.

Fill the crust: Pour the lime mixture into the slightly cooled graham cracker crust. Gently tap the pie plate once on the counter if you see large bubbles on the surface.

Bake the pie: Bake at 350°F (175°C) for about 15 to 20 minutes. The edges should look set while the center should still have a slight jiggle when the pie is gently moved. The filling should reach at least 160°F (71°C) in the center for food safety.

Cool completely: Remove the pie from the oven and place it on a wire rack. Let it cool at room temperature for about 1 hour. The filling will continue to firm as it cools.

Chill until firm: Cover the cooled pie and refrigerate for at least 3 hours, preferably 4 hours or overnight. The center should feel firm when gently pressed.

Prepare the optional whipped cream: Just before serving, beat the cold heavy cream, powdered sugar, and vanilla until medium-stiff peaks form. The cream should hold its shape but remain smooth.

Slice and serve: Cut the chilled pie into 8 slices using a sharp knife. Wipe the knife clean between cuts for neater slices. Top each serving with optional whipped cream and lime zest or a thin lime slice.

Chef: Use room-temperature egg yolks for a smoother filling.

Chill the pie thoroughly for the best texture before slicing.