01 -  Preheat the oven to 175°C (350°F). 
 02 -  In a medium bowl, combine graham cracker crumbs, sugar, and melted butter. Mix until the texture resembles wet sand. 
 03 -  Press the mixture firmly into the bottom and up the sides of a 23 cm (9-inch) pie dish. 
 04 -  Bake the crust for 8 minutes. Remove and let cool slightly. 
 05 -  In a bowl, whisk egg yolks and lime zest for 2 minutes until slightly thickened. Add sweetened condensed milk and whisk until smooth. Gradually whisk in key lime juice until fully combined. 
 06 -  Pour the filling into the prepared crust and smooth the top. 
 07 -  Bake for 12 minutes, until the filling is just set but still slightly wobbly in the center. 
 08 -  Remove from oven and cool to room temperature, then refrigerate for at least 3 hours or overnight until thoroughly chilled. 
 09 -  Whip heavy cream with powdered sugar and vanilla extract until soft peaks form. 
 10 -  Spread or pipe whipped cream over the chilled pie before serving.