Preheat oven to 275°F and line a muffin tin with cupcake liners.
Place an Oreo cookie at the bottom of each liner.
In a large bowl, beat cream cheese and sugar until smooth.
Mix in vanilla, eggs, sour cream, and salt until combined.
Divide the batter evenly among the liners and bake for 20-22 minutes.
Cool completely before adding the ganache.
To make ganache, heat heavy cream until hot but not boiling.
Pour over chopped chocolate and stir until smooth.
Spoon ganache over cooled cheesecakes and chill until set.