Preheat oven to 350 degrees F (175 degrees C).

Melt butter.

Combine melted butter, sugar, and graham cracker crumbs in a bowl.

Mix thoroughly until well combined.

Press the mixture into the bottom and sides of a 10-inch pie tin using your fingertips.

Bake the crust for 8-10 minutes, or until lightly golden. Watch carefully to prevent burning.

Remove the crust from the oven and let it cool slightly.

In a separate bowl, combine Key lime juice, sweetened condensed milk, egg yolks, whole eggs, and lime zest.

Blend until smooth and creamy.

Pour the filling into the pre-baked graham cracker crust.

Bake at 350 degrees F (175 degrees C) for 35 minutes, or until the filling is firm.

Remove the pie from the oven and let it cool completely.

Refrigerate the pie for at least 1 hour before serving.

Serve chilled with a dollop of whipped cream and fresh lime zest. A mango puree sauce on the serving plate is optional.