Pre-heat oven to 275°F.
Line a muffin tin with cupcake liners.
Place an Oreo in the bottom of each one.
In a large bowl, beat the cream cheese and sugar together until smooth.
Beat in vanilla extract, eggs, sour cream, and salt.
Continue beating until combined and smooth.
Add a heaping tablespoon of cheesecake batter to each muffin cup.
Warm the hot fudge sauce in the microwave for 20 seconds.
Place a scant teaspoon of hot fudge into each cupcake.
Add another tablespoon of cheesecake batter on top, filling the cupcake liner.
Use a toothpick, or butter knife, to gently swirl the fudge into the cheesecake mix.
Bake in the pre-heated oven for 22 - 25 minutes until filling is set.
Cool completely, in the tin, before removing.
Store in refrigerator.