1 1/4 cups graham cracker crumbs from 9 (2 1/4-inch by 4 3/4-inch) crackers
2 tablespoons sugar
5 tablespoons unsalted butter, melted
1 (14-ounce) can sweetened condensed milk
4 large egg yolks
1/2 cup plus 2 tablespoons fresh or bottled Key lime juice (if using bottled, preferably Manhattan brand)
3/4 cup chilled heavy cream
1. Preheat oven to 350°F.
2. Stir together graham cracker crumbs, sugar, and butter in a bowl with a fork until combined well, then press mixture evenly onto bottom and up side of a 9-inch (4-cup) glass pie plate.
3. Bake crust in middle of oven 10 minutes and cool in pie plate on a rack. Leave oven on.
Make filling and bake pie:
1. Whisk together condensed milk and yolks in a bowl until combined well. Add juice and whisk until combined well (mixture will thicken slightly).
2. Pour filling into crust and bake in middle of oven 15 minutes. Cool pie completely on rack (filling will set as it cools), then chill, covered, at least 8 hours. Pie (without topping) can be chilled up to 1 day.
1. Just before serving, beat cream in a bowl with an electric mixer until it just holds stiff peaks. Serve pie topped with cream.