3/4 cup key lime juice or freshly squeezed lime juice (4 to 5 limes)
1 1/2 cups graham cracker crumbs (8 crackers)
1/4 cup granulated sugar
6 tablespoons unsalted butter, melted
1 cup granulated sugar
1/2 cup water
4 egg whites, at room temperature
1/2 teaspoon cream of tartar
1/2 teaspoon vanilla extract
1 lime, sliced into thin slices
5 hours, 30 minutes
1. Line a 8-inch bread or terrine pan with plastic wrap, leaving a 6 inch overhang on all sides. Set aside.
2. Make the Filling - beat the egg yolks and sugar on high speed in the bowl of an electric mixer fitted with a paddle attachment for 5 minutes, until thick. With the mixer on medium speed, add the condensed milk, lime zest, and lime juice. Pour into the prepared pan and freeze for 1 hour. Do not cover with plastic wrap.
3. Make the Crust - combine the graham cracker crumbs, sugar, and butter in a bowl. Spread the mixture over the filling in even thickness, creating a ½ inch crust. Using the overhang wrap the crust with the plastic wrap. Freeze at least 4 hours or overnight.
4. Make the Meringue Topping: in a small saucepan, combine sugar and water. Heat over high heat, brushing down sides of pot as necessary with a pastry brush dipped in water. Cook until sugar syrup registers 240°F on an instant read or candy thermometer.
5. Meanwhile, combine the egg whites and cream of tartar in the bowl of a stand mixer fitted with a whisk attachment. Set mixer to medium speed and mix until soft peaks form (when lifted, the head of the mixer should form gentle peaks in the egg whites that very slowly collapse back into themselves), about 2 minutes.
6. With the mixer running, slowly drizzle in hot sugar syrup. Increase speed to high and whip until you have stiff peaks, about 6- 8 minutes.
7. Decorate: Remove the pie from the freezer. Unwrap the plastic overhang and lay the serving plate upside down and on top of the pie. Gently flip over the plate and the pie, removing the pan. Add the meringue in large spoonfuls to create wispy arcs. If desired, use a torch to gently brulee the meringue. Cut into slices and serve with lime wedge. Store in the freezer.