To make the crust: Pulverize the graham crackers in a food processor, then add the butter, sugar, and salt and blend until incorporated. Press the mixture into a pie plate, so it is even all the way around. I used a deep pie plate, so I didn't go all the way to the top. It should be about 1/8-inch-thick throughout. Bake the crust for about 15 minutes or until it is golden brown and smells toasty.
To make the filling: If your cream cheese isn't soft enough to whisk, heat it for 10 seconds in a microwave. Whisk the cream cheese and sugar until smooth. Whisk in the sweetened condensed milk, yolks, key lime juice and salt. If the mixture is lumpy at all, strain. Pour the mixture into prepared crust.
Bake for about 25 minutes, or until it is set like jello when you jiggle the pan.
Prepare the curd as the filling is baking. Whisk together all the curd ingredients except the butter in a large metal bowl. Place the bowl over a pot of gently simmering water set up as a double boiler. Stir constantly with a rubber spatula until the curd begins to thicken, about 10 minutes. Add the butter and continue to stir until it is completely melted and the curd is quite thick; it will be the consistency of smooth pudding. If there are any lumps, strain the curd into a container; then cover with plastic wrap and place in the freezer until cool. Then refrigerate.
Once the filling is set, let it sit for about 10 minutes, then gently spread the curd over the top of the filling and bake for an additional 5 minutes. If you made your curd ahead and it is chilled, stir well, so it isn't too stiff, then bake for 8-10 minutes.
Let cool on a wire rack for 15 minutes and then refrigerate until well chilled, at least 2 hours.
Just before serving, whip the cream, sugar and vanilla to medium peaks. Spread it or pipe it over the top. Use a sharp knife dipped in hot water to slice.
Want to make the candied lime slices? Find the recipe above in my blog post.