For the Crust:

7 tbsp. butter, melted
1 1/2 c. graham cracker crumbs (about 10 crackers)
3 tbsp. sugar

For the Filling:

4 pasteurized egg yolks or regular egg yolks
1 (14 oz.) can sweetened condensed milk
1/2 c. Key lime juice (8 to 10 Key limes)
1 1/2 c. heavy cream
2 tbsp. sugar

For the Crust: Preheat oven to 375°F. Butter a 9-inch glass pie plate with some of the melted butter and set aside. Combine graham cracker crumbs, sugar and remaining melted butter in a medium mixing bowl, then transfer to prepared pie plate. Spread crumbs evenly on bottom and up the side of the pie plate, then using your fingertips, firmly press down on crumbs to form a crust.

Bake crust until lightly browned, about 10 minutes. Remove crust from oven and set on a wire rack to let cool to room temperature.

For the Filling: Briefly whisk egg yolks in a large mixing bowl, then gradually add condensed milk, whisking until smooth. Add lime juice and mix until just combined. Pour filling into prepared crust (filling will thicken as it sits). Cover pie with plastic wrap, being careful not to let it touch the surface of the filling, and refrigerate until well chilled, at least 6 hours or overnight.

Just before serving, put heavy cream and sugar into a large, well chilled mixing bowl. Beat cream with a whisk or an electric beater on high speed until cream just forms soft peaks (do not overbeat). Decorate pie with large dollops of whipped cream and thin slices of Key lime.