For the Crust
In a medium bowl, combine the graham cracker crumbs, sugar, salt and melted butter. Stir until mixture resembles wet sand. press the crumb mixture into a 9-inch springform pan, spreading it 11/2 to 2 inches up the side. Chill crust in the freezer for 15 minutes. Alternatively, you can bake the crust at 350F for 10 minutes, and let cool.
For the Filling
Melt the chocolate in a heatproof bowl set over a pan of simmering water (double-broiler). Stirring occasionally until chocolate melts and is smooth and glossy. Carefully, remove from heat, and avoid getting any water in the bowl.
To make the filling, in the bowl of a stand mixer with the paddle attachment, on medium speed, beat the softened cream cheese until smooth. Add the condensed milk and vanilla, beating on low until combined.
Pour the filling over the chilled crust, and spoon the melted chocolate on top. Using a skewer or knife, make swirls in an 8-figure motion, going around the filling 2-3 times.
Cover with plastic wrap and place in the fridge for 2-4 hours before serving.