Preheat the oven to 350°F.
For the crust, Add the finely crushed graham crackers and melted butter to a bowl and stir to combine. Press this mixture into the bottom and neatly up the inside of the prepared pie dish, using the ball of your hand or the back of a tablespoon to flatten and compress it.
Bake in the preheated oven for about 20 minutes, or until the crust looks baked and the bottom feels firm. Set aside to cool completely.
Turn the oven down to 300°F.
Put the egg yolks, condensed milk, and lime juice and zest in a glass bowl and whisk gently with a balloon, whisk until all the ingredients are very well incorporated. The mixture will thicken naturally.
Pour into the cooled pie crust and bake in the preheated oven for 20-30 minutes. The filling should be firm to the touch but still very slightly soft in the centre (not wobbly). Let it cool completely, then cover and refrigerate for at least one hour, or overnight if possible.
When you are ready to serve the pie, whip the cream with an electric hand mixer in a large bowl until soft peaks form, then spread over the pie and decorate with a little lime zest.