Preheat oven to 350 degrees F. Combine graham crumbs, sugar and melted butter in a medium sized bowl.
Press into the bottom and up sides of a 9 inch glass pie plate or similar sized tart pan. You can use your fingers or gently use a small glass.
You have a bit of flexibility with the size of dish. Bake for 8 minutes, or until golden brown and fragrant. Cool completely.
For Filling
In a large bowl, whip heavy whipping cream with sugar until somewhat stiff peaks form. Be careful not to overwhip it into butter! Set aside.
In another large bowl, whip condensed milk on medium speed until it appears fluffy. Slowly add freshly squeezed lime juice (this was the juice of 4 limes for me).
Continue to whip until the mixture is light and well-combined.
If you microwave each lime for 15 seconds before juicing you will get more juice. I don't know why, but it's true!
Gently fold the whipped cream into the lime mixture, being careful not to squash the fluffiness.
Spread on top of cooled graham cracker crust and refrigerate at least two hours to set. This can even be made a day ahead of time.
For Topping
Before serving, top with additional whipped cream (at least 1/2 cup of cream whipped with 1 teaspoon of sugar) and lime zest (optional). Enjoy! :)