Spray a 10-inch pie plate with cooking spray and set it aside. A light coat of spray is all you need; this keeps the crust from sticking when you slice and serve.
Add graham crackers to a food processor and pulse until you have fine, even crumbs. You want them uniform; coarse crumbs will give you a crumbly crust that falls apart when you cut it.
2 sleeves graham cracker crumbs
Transfer the crumbs to a mixing bowl and stir in the sugar and salt. Add melted butter and mix until the crumbs look like wet sand and hold together when you press them between your fingers. If the mixture still crumbles loosely, add a small drizzle more of melted butter.
2 Teaspoons Sugar, ¼ Teaspoon Salt, ½ Cup Butter
Press the crumb mixture firmly and evenly into the bottom and up the sides of the prepared pie plate. Use the flat bottom of a measuring cup to press and compact it; a loosely pressed crust will not hold its shape when filled. Place the crust in the freezer for at least 10 minutes while you make the filling.
In a large mixing bowl, beat the softened cream cheese with a hand mixer on medium-high speed until completely smooth and creamy; about 2 minutes. This step matters. Any lumps in the cream cheese at this stage will still be lumps in your finished pie.
24 Ounces Cream Cheese
Add the sweetened condensed milk, lime juice, and lime zest. Beat on medium speed until fully combined and smooth. The filling will be thick and pourable.
14 Ounces sweetened condensed milk, ¾ Cup fresh lime juice, 1 Teaspoon lime zest
Using a rubber spatula, gently fold in the thawed Cool Whip or homemade whipped topping. Fold, do not stir; stirring will deflate the whipped topping and give you a denser filling.
8 Ounces Cool Whip
Remove the crust from the freezer. Pour the filling into the crust and spread it evenly with an offset spatula or the back of a spoon. Work from the center out, pressing lightly to remove any air pockets.
Cover the pie loosely and refrigerate for at least 4 hours, or overnight. The filling needs this time to set up firm enough to slice. Overnight is the better option; the lime flavor deepens considerably.
When ready to serve, pipe or dollop whipped cream over the top and finish with fresh lime zest and lime slices. Slice with a clean, sharp knife, wiping the blade between cuts for clean edges.
Whipped cream, Lime zest