Mix together graham cracker crumbs, melted butter and sugar in a bowl.
Pour the mixture into a 9 inch pie plate and press down into the plate and around the sides. Bake for 10 minutes to set.
For the Filling:
Whisk together egg yolks, key lime juice, condensed milk, and vanilla extract.
Pour filling into baked pie crust.
Next carefully spoon drops of melted raspberry preserves (make sure they are just melted) over filling. Using a butter knife or skewer, drag the knife through the drops creating a swirl pattern in the filling.
Bake for 15 minutes until set then let rest until it cools to room temperature.
Refrigerate for 2-3 hours, garnish with whipped cream and berries if desired and serve.
Make sure you do not use regular lime juice for this recipe. Buy key limes and squeeze juice or use store bought key lime juice.