Prepare the Crust:
Mix graham cracker crumbs, sugar, and melted butter in a medium basin. Press the mixture into the bottom and up the sides of a 9-inch pie plate to make the crust. Press it down with a spoon or flat-bottomed glass. Set the crust in the fridge while making the filling.
Make the Filling:
In a large mixing bowl, whisk together the sweetened condensed milk, key lime juice, and lime zest until well combined. Set aside.
Whip the Cream:
In a separate bowl, using an electric mixer, whip the heavy cream, powdered sugar, and vanilla extract until stiff peaks form. Be careful not to over-whip.
Fold in the Whipped Cream:
Gently fold the whipped cream into the key lime mixture until well combined. Use a spatula to ensure a light and airy texture.
Fill the Crust:
Retrieve the pie crust from the refrigerator. Pour the key lime filling into the prepared crust, spreading it evenly with a spatula.
Cover the pie with plastic wrap and refrigerate for at least 4 hours or overnight. This allows the pie to set and the flavors to meld.
Garnish and Serve:
Before serving, you can garnish the pie with additional lime zest, slices of lime, or whipped cream for an extra touch. Slice and serve the dreamy, no-bake Key Lime Cream Pie chilled.