4 large egg yolks
4 tsp. grated lime zest
1 (14 oz.) can sweetened condensed milk
1/2 cup fresh lime juice (5 limes)
1 1/4 cup graham cracker crumbs
5 tbsp. unsalted butter, melted
2 tbsp. sugar
1 cup heavy cream, chilled
3/4 cup confectioners' sugar
1. Move oven rack to lower-middle position and heat oven to 325 degrees F.
2. For the filling: Whisk the yolks and zest together in a medium nonreactive bowl (stainless steel, glass, or ceramic) until the mixture has a light green tint, about 2 minutes. Whisk in the milk until smooth, then whisk in the lime juice. Cover the mixture, then set aside until thickened, about 30 minutes.
3. For the crust: Toss the graham cracker crumbs, butter, and sugar together thoroughly with a fork. Pour the crumbs into a pie plate. Use the bottom of a measuring cup to press the crumbs into an even layer on the bottom and side of the pie plate. Bake until the crust is fragrant and beginning to brown, 15-20 minutes. Leave the oven at 325.
4. Pour the thickened filling into the warm pie crust. Bake until the center is firm but wiggles slightly when jiggled, 15-20 minutes. Transfer the pie to a wire rack and cool to room temperature, then refrigerate until well chilled, at least 3 hours.
5. For the topping: Just before serving, whip together the cream and sugar in a chilled bowl until soft peaks form. Spread whipped cream attractively over the top of the pie.
*From America's Test Kitchen