To create the base for your Key Lime Pie Trifle, combine 1 cup of graham cracker crumbs with 4 tablespoons of melted unsalted butter in a mixing bowl. Stir until the crumbs are evenly coated. Press this mixture firmly into the bottom of a clear serving dish or trifle bowl, creating an even layer. Reserve ½ cup of crumbs for layering and topping later.

In a large mixing bowl, add 1 cup of chilled heavy whipping cream. Using a handheld or stand mixer, beat the cream on medium-high speed until stiff peaks form, which should take about 3-5 minutes.

In another mixing bowl, beat 8 ounces of softened cream cheese until smooth and creamy, about 2 minutes. Gradually add ½ cup of powdered sugar, ¼ cup of fresh key lime juice, the zest of one lime, and 1 teaspoon of vanilla extract. Continue beating the mixture until fully combined.

Carefully fold the whipped cream into the cream cheese mixture using a spatula. Start by adding one-third of the whipped cream to lighten the mixture, stirring gently. Once combined, gradually fold in the rest.

Spread half of the creamy lime filling over the prepared graham cracker crust in your dish. Sprinkle a portion of the reserved graham cracker crumbs over the filling. Repeat this layering process with the remaining lime filling, finishing with a layer of reserved graham crumbs on top.

Cover the assembled Key Lime Pie Trifle with plastic wrap and place it in the refrigerator. Allow it to chill for at least 2 hours to let the flavors meld together.